That’s quite a bit slower to process. At least if you’re converting to integers to do the calculations and the calculations would be quite a bit slower if you kept the big decimal type

True, but this is usually your least concern when you're dealing with monetary amounts/math.

It might be your least concern, and that's fine but it's not the least concern for many people who need to process large volumes of transactions.

Money, even within fintech, is a concept used across a wide variety of domains, and you can't assume that what concerns you is what concerns everyone else relying on it elsewhere.

They specifically mentioned HFT so I suspect they care a lot about processing speed