I can't speak to whether this is actually true or not, but I can talk about flaws in the methodology used in the map you linked. There's a very important quote from the article:

They found 12,703 battles which had an exact location and date, 2,657 of them are from Wikidata, the others are from DPpedia.

So they only used battles that could be accurately dated and located. This creates a bias towards areas with a greater written historical record. The data itself is also pulled from wikipedia/DPpedia, which isn't exactly a scholarly source and may have a Western bias in results.

Then there's also an issue with defining a "battle." Constant skirmishes and raids for resources were commonplace in areas like Central Asia, where the map is nearly blank. Does 150 raiders showing up and stealing livestock/killing 50 people get included in this data? I doubt it, or the map would be one giant splotch. That's no less "bellicose" than a more formal war being fought in Europe.

All this map really tells us is that the data they were able to pull shows that Europe has more instances of historically recorded battles than the rest of the world during this timespan.

It's a neat map, but one with too many issues in how the data was collected and holes in that data to be more than something fun to browse.

I've never seen in-depth scholarly research done on this sort of thing, usually just pop-history for clicks or something to start a discussion. The problem is there's an enormous amount of data required with huge holes in written history in large parts of the world that make a definitive answer impossible.

Adding on to what /u/stylepointseso pointed out about the methodology, I can offer one historian's - Tonio Andrade - view on the matter. In his book, The Gunpowder Age, which compares gunpowder and firearms development in China and in Europe, Andrade addresses the wide-spread belief that 'anatgonism between European states...exerted a selective pressure on European socieites' while 'China, on the other hand had a unified imperium, which impeded experimentation and led to stasis.'

He also makes note of the fact that some scholars have pointed towards the Confucianism as another reason for the relative peace in China versus the chaos and violence of Europe down to WW2. Confucianism, they argue, is doctrinally opposed to violence and that stymies the outbreak of war.

While it is true that Confucianism is against violence, so too is Christianity and that's never stopped anyone. Further, as Andrade shows later in his book, many of the principal Chinese military innovators in the Early Modern era were Confucians, so the argument doesn't really hold water.

Early in the book Andrade notes that 'there were many others periods of warfare and interstate competition in China's long history, and scholars have tended to neglect those times and exaggerate China's imperial unity.' Andrade goes on to argue that while China did see 'periods of great unity', particularly during the Ming and Qing dynasties, the dynastic transition periods were 'periods of intense warfare'. In terms of the Ming dynastic transition alone - lasting from around 1350 to 1450 - the wars were 'frequent, intense and of a scale far exceeding anything in Western Europe at the time, with armies of hundreds of thousands clashing throughout East Asia'.

Was China more violent than Europe? Andrade provides a graph in the book (which unfortunately I can't get up for you here but it's on p.6 if you ever get the book) which shows, essentially, sometimes yes, sometimes no. There are periods in which Europe enjoys relative peace while China enjoys relative turmoil and vice-versa. Part of the problem here is also where do you draw the line? Do we compare China and Europe from 0 AD to 1945 or do we go from the beginnings of human history?

Personally I don't think it actually matters where one draws the line. Even if we looked at all human history and found that Europe had 11 conflicts in its history and China had 10, I don't think that necessarily makes the Europeans more warlike. If Europe had 100,000 and China had 3 that would be another situation, but I would wager (and this is purely conjecture) that the amounts of conflicts (however you wish to define 'conflict') in all the major regions of human civilisation throughout human history are going to be comparable. If one region has slightly more conflicts that doesn't necessarily mean they're more warlike.

Andrade's book is telling though. It has been a widespread view that Europe was much more fractious and instable than China - and indeed, that this was a good thing for Europe because it made the Europeans just so good at war - but I agree with Andrade in saying that this, probably, wasn't true.

Sources:

Andrade, Tonio. The Gunpowder Age: China, Military Innovation and the Rise of the West in World History, Princeton University Press (New Jersey, 2016)