Those two are not related.
Opening a chest through normal gameplay is not an exploit. That however does not mean that items gained through a bug should not be rolled back either.
It not being an exploit merely means nobody should be banned for it.
Indeed.
Whether it is important to fix is an opinion I guess.
But just on pure principle, bugs should be fixed. No need to arbitrarily decide if it is big enough or not. It should just be fixed because that is what you do with bugs. Hopefully.