is HR zone 3 Aerobic or Grey Zone?

setting up my HR zones based on LTHR test that i did for myself (warmup 10 mins, run all out for 20, take avg of last 20 mins ans that is your LTHR and then back up the %) my watch is telling me that Zone 3 is aerobic zone and obviously counts a lot towards aerobic progress.

yet anywhere i read online, and even the automated plans that garmin provides you, everything is saying that one should run in zone 2 "easy" and zone 3 is a grey no-mans land and should only be run in 10% of all your running times.

shouldn't garmin then be calling it something else and not an Aerobic zone, aerobic zone to me means that you should do all your excercise in zone 3.

where am i getting confused?