It’s mainly due to the technique used and how printing took place, I can’t speak to gold bars but I imagine a similar technique would have taken place.

The actual shape of coins was mostly irrelevant in the Ancient world and the medieval world up until fairly recently. The weight of the coin was really the only thing that mattered. Coins could be used from different places as long as they retained the same mixture of metals and had the same weight. Coins in the ancient period could have been melted down and remade into newer coins.

Minting coins isn’t exactly cheap as the only place it could occur is a mint which (sometimes) had the facilities to cut down the metals but also needed to heat the coins up and use a created mold to impress upon the dies where the blank flan would be struck between the two dies and the Obverse and the Reverse of coin would be imprinted.

Given that most coins can be fairly well identified in imperial Rome where we can for the most part tell which coins were printed in the same batch as other coins is primarily because they used the same mold and die imprints.

It is very very difficult to create a mold and even harder to make a perfect one as they were usually made from stone or other resilient rocks. Even the most skilled artisan couldn’t align text perfectly. As such if the mold wasn’t perfect in it’s alignment then all the coins would reflect that.

That’s not to say that all coins from the same mold look the same as often there are minor differences in things such as the depth of the imprints.

As the shape of the coin changed from coin to coin even with gold coins, the print of the coin would often end up in different places if that’s what you mean by unofficial or unprofessional but I feel like you’re talking about how they often appeared out of line. That again is due to the printing more or less being an identifier as opposed to conveying anything other than why or where something was minted. The mint would be happy with the product unless half the print was somehow missing (many coins have edges of the print of the side but they were considered fine) or the weight was off and the value of the coin was diminished a result.

First, we can't know what "professional" meant to the Roman eye. With the Gold bar, those stamps might have just been quick and dirty ways to mark for inventory and quality control.

With the coin, a Republican issue (pre-Augustus), you usually see the same lettering format. Which makes me think it was the style. But that aside, there is a huge amount of skill to carve a die to produce a bust like that on the obverse.

Here's an example from the 330's. Struck at the rate of a million a day in total from the dozen some mints active during the 330s. If anything would qualify as "low production, get it done and out the door we don't care about quality" it would be a coin like this.

Yet look at the detail and precision still visible after being buried for 1700 years.

Or this from Emperor Probus circa 280 The size of a quarter. Look at the details on this including the shield on his shoulder showing him on horseback spearing an enemy.

And this also from Probus. Check out the detail in the helmet and beard on this one.

Of course, they weren't perfect given that the coin blanks were created by hand and then struck by hand. But they were far from janky.