I will try to tackle this question with you but I will have to tell you in advance that I find it very difficult to articulate an answer in a foreign language here. This is a problem that originates from our understanding of disciplines, complexity and history of ideas and I am used to writing about political economics, so my vocabulary might be lackluster.

How this very common phenomenom emerges might become clearer to you when we take a look at how we construct knowledge, especially how historical knowledge, that can be interpreted and in some way or form, becomes a temporary "truth". In your context the observation that something caused working days to become shorter while wages were rising during a similar timeframe, becomes subject of a academic discpline, because someone decides to describe and analyze it. What an academic discpline is, is to this day a heavily discussed topic. A common definition at least requires A) an object of research B) a body of accumulated knowledge specific to the research object C) a toolset of theories, concepts, models and language to analyze the research object and organise accumulated knowledge and D) is institutionalized in an academic setting (What are Academic Disciplines?, Krischnan 2009: 9).

This, by design, creates a methodical reduction, narrows down the possible approaches to finding an answer within a specific discipline and frames a problem within that structure. While this can be problematic, it is also a very helpful tool to reduce complexity and allowing new observations. The accumulated knowledge helps to create educated guesses which can then be analyzed further until a more complete form of knowledge emerges. While along the way often wrong theories and observations emerge, in the end, none of the two methodologies is more right then the other. Ones result might be more right in a specific circumstance, but most of the time it is simply the point of view or the scope the differs. This is a very important and reoccuring topic within every discplinie, because for many complex problems reductionist approaches have proven to be futile. They can prevent academics from seeing close connections to other bodies of knowledge or might cause wrong interpretations because some problems might be irreducible in their complexity.

In recent years there has been a massiv surge of interdisciplinary studies and interdisciplinarity has become a very common scientific philosophy for many academics. But also many disciplines have gone through massive internal changes. Lets take economic history in germany for example. After the second world war, economic history was heavily influenced by cliometrics, the use of mathematic economic methods to study history. While some of these methods are still being used, the toolkit of economic history now also is heavily connected to other social sciences again, drawing from historical institutionalism, cultural theories, innovation studies and especially political science theories about power and global governance. For example you can take a look at the ever emerging theories about globalization. As an economic historian I can simply take a look at the 3 important costs of globalization for business:

• transport costs of goods (start falling early during the agricultural and industrial revolution)
• transport costs of people (start falling early but remain problematic to this day, because a worker on voyage does have huge costs of opportunity)
• transport costs of information(start falling very slowly and then suddenly during the ICT-Revolution)

and get a pretty good understanding of what enabled globalization and especially the different phases of globalization (for a decent overview you might want to take a look at Richard Baldwins: The Great Convergence). But for a more complete understanding of the processes, I also need to take a look at not only the economic situation but also the institutions and political / cultural mentality that frames every market. This is why concepts like functional convergence (the idea that exogenous and economic shocks empower private and public economic stakeholders to create and use formal or informal institutions to further their common agenda by aligning their goals), different concepts of power and epistemes have become valuable tools. They allow us to connect bodies of knowledge of different disciplines, judge them against each other and keep the complexity without making a topic unapproachable. We can then focus on interdependencies or forces in opposition to each other instead of focusing on top-down or bottom-up, down-stream or up-stream causation. Considering your example, if we want a complete understand of how and why shorter working days and higher wages became a thing during a specific timeframe, we can take into account our economic history knowledge about the rising productivity and technological innovation to create a framework in which we can then analyse what allowed workers to gain the necessary political power to demand higher wages and lower working hours and under which circumstances those demands were met. But we can also go in the opposite direction and use the political climate of worker movements and the new structural factors created by it as our framework to ask what economic incentives and constrains might contribute to the rising productivity and how we might be able to prove such a connection.

I hope I was able to give you a half-decent answer to your question. If you have any follow up questions, please let me know.

On a last Off-Topic sidenote: If you want a better understanding of why this is such an important topic and you are open to taking an interdisciplinary step into philosophy you might want to take a look at Michel Foucaults famous "The Order of Things" (I do not know if it is as good in english though, foucault can be tough to wrap your head around). He goes into more depth on this topic in his "Technologies of the self" and "Discipline and punish", but he has some very extreme conslusions and you have to make your own judgement on many of his ideas. In my opinion a very important read that might change your view on economic history and history relating to regulation are his lectures called "The Birth of Biopolitics", which are in my opinion simply brilliant.