Well, they are databases. That doesn't imply accountants don't understand accounting. Both can be true.

I think a large factor in the "programmers reinterpreting accounting" phenomenon is the fact that accounting is full of somewhat idiosyncratic terminology and conventions which are somewhat counter to modern mathematical conventions. These conventions should still be upheld in order to be mutually intelligible with the accounting world, but it seems quite unlikely they are the optimum in terms of ergonomics and ease of understanding. If we designed accounting from scratch today, I doubt we would end up with these conventions.

A naive programmer is perhaps in one of the best positions to see these idiosyncrasies and think "This is using the wrong conventions and can be made much simpler by just shifting some signs around!".