maybe synchro gears? hard to say.
my frame of thought is this. Usually for items like this they can't really service it and treat the tranny as a single replacement unit which is very costly for them to replace on a hunch of a problem. Secondly I find the more mechanics take things apart new and different problems arise. Not that the mechanics are bad or anything but most times things are forgotten or not done correctly as the car is very very tight to work in/around. Not ideal conditions compared to at the factory where even the car is rotated on it's side to gain easier access.
if it's not causing any problems I'd wait and see if real problems arise such as not being able to get it into gear before getting it serviced. you have a long way to go before CPO runs out.
You should however note the issue with the service advisor so it's on record that you noticed an issue and gain their agreement that something is not right. I think they would be more willing to do that than go on a hunt for the problem which is time consuming for them and possibly create other headaches for you.