The powertrain warranty is still in force (5yr/100k miles) so, if it is at a chevy dealer there should be no concern about who pays.
That being said, this trans can do some weird things that take some getting used to. The partial neutral re-engagement when releasing the brake is one of them. The manual tells you about it but it really could have more ink......kind of a vague description.
This trans often displays a rather harsh third gear engagement.....usually when cold, usually just one time.....then no replay till the following day. Other than make you think you broke it, seems to cause no harm.
Another strange characteristic is on throttle reapply after making a rolling turn.....say about twenty mph.....the torque converter unlocked during the turn and then does this lazy......lazy reapply......does sound like a slipping trans though.
This 'flare' you have experienced has not come up or possibly you are more sensitive than most......can you see the tach. rise in conjunction with the flare?
Since the warranty should still be 'live' (get the service department to print the info based off your vin#) I believe time is on your side to get it to misbehave more frequently.