Another little inconvenient: Try doing your little trick below 100 feet, and that's where most of us would be likely to do it to save the landing, and with the fantastic AB logic ..... you end up with GA thrust!!!! Definitely not what you intended methinks.
Actually, below 100' AGL if you move the thrust levers forward of the CLB detent the A/THR disconnects. To select TOGA or GA thrust as you call it, the thrust levers must be moved into the TOGA detent (except in the case of alpha floor protection of course).