Yikes..

It's not the professors job to make assignments unique.

Yeah it is.

The goal is whatever the goal is. And it's never to copy paste from another class.

Unless explicitly stated I see no issue. If professors don't want this to happen maybe they should coordinate instead of assigning work that can be used again and again.

As for your last part, it's not some gotcha professors use to ruin students time. It's in every university's plagiarism guide.

It 100% is because they using the word plagiarism when everyone knows that it doesn't fit the definition of plagiarism. It is a made up charge and only serves to set someone up to be expelled. If you want to have rules around it, fine, but don't try to call something it isn't.

/r/facepalm Thread Parent Link - i.redd.it