Why is the whole belt tensioner assembly is replaced if the tensioner bolt was turned counter-clockwise?

[MalcolmY]

Today I replaced a belt tensioner pully/bearing on another car. I removed and replaced that pully/bearing very easily with zero problems. It was just one single bolt.

Why does Nissan caution not to loosen that bolt on the Altima? Couldn't it be just tightened again? The FSM really doesn't explain anything.

I read this caution here and on EM-16 in the FSM:

quick-how-to-drive-belt-change-on-l32-a ... 79969.html

[AZhitman]

I suspect it has something to do with the alignment of the pulley on the shaft... if the bolt is loosened, the bearing / shaft could misalign and wreck the tensioner.

I've never had an issue with one either, but I'm sure the factory has their reasons.