You know what's worse than being not having a perfectly accurate representation of something?

Being told that something is working when it has crashed and you'll only notice it after a long, unknown time because the damn output is lying to you.

So the user knows if they should stop waiting, reload/refresh/restart, or just hang tight.

If a progress bar or loading animation does not stop when something goes wrong, the it is conveying zero information and shouldn't be there.

Because you want to know if there was an error during loading and it's not progressing anymore, instead of a forever-increasing loading bar that just makes you wait.