It’s because you forgot a comma after the last item. If you had kept that the items wouldn’t have been compacted (at least in black, I’ve stopped linking my code because it breaks intends of formatting more often than it helps)
foo=[baz, bar,]
returns a nice list of two items, but if you edit this down and miss the comma,
foo=bar,
is not a scalar.
returning a tuple.
So the trailing comma thing is a thing.
Taking that as a reason to not have those rules in the first place seems like a logical fallacy that intelligent people should not make.