I live in a town where a somewhat well-known instructor also resides, and I went to a few pistol classes with him. He has a "9mm only" rule for the students and I had to negotiate a special dispensation. We found that my G42 can run a 1300-round count class with no issue. However, I understood that good reasons existed for students not to get too clever. For one, some drills involve dummy cartridges, and students have to be careful not to mix 9 and 380 as they are reused. Also, shooting of steel targets at short range requires frangible ammunition, not available in .380. So yeah, the littliest Glock is a real Glock, but in the same time it's not the same as the rest.
I mostly use my G42 with +2 extensions and I wish Glock just made a G42X with compatible magazines. The G43X has its own magazine, but IMHO that is excessive for G42. I would be happy to buy a 8-round G42X.