Yes this is absolutely how Linux operates, but it's embarrassing and primitive, and it's actually decidedly a bug.
I haven't done much programming for many years, but you used to be able to see if you went a step deeper into the file system operations, whether the file you are copying still has parts in cache.
Just because nobody does it, doesn't mean it's not a bug.
There is no sense in showing a progress bar that is wrong anyway.