I don't think it's been deconstructed so much as it has been re-branded. Coaching has always been and remains a perfectly accurate term to describe, well... coaching.

It seems to me that the current meaning of "mentor" is the result of the term's (mis)use by VCs and accelerator programs to make coaching sessions seem like something more than they really are.

I've never heard the term "sponsee" used in this context, but like I said, meanings change pretty fast, don't they?