Especially with the M2 and upcoming M3, there will be a lot of folks for whom the M# processors provide more than enough processing power, but still need a larger screen (e.g., those doing spreadsheet work). A 15" M# Air would be perfect for them.
It does make sense to disconnect processing power and screen size (i.e., not require those who just need more screen size to purchase a Pro/Max), since these really are two separate requirements.
The one key potential downsize of a 15" M2 Air to a buyer is that Apple continues to nerf the non-Pro/Max chips by limiting them to 2 monitors (which means one external for the notebooks). I.e., the very people that would buy an M2 are those that need more screen real estate. Yet when those same people use that device at home, they'll be screen-limited to one external display.
That of course won't be an issue for some potential 15" M2 Air buyers, but it will be for others.
This is the one key way in which, even with a 15" M2 Air, Apple will not have separated processing power and screen real estate requirements.
[Though if it's coming in 2023, it will probably be an M3 Air, with A16-based microarchitecture and an N3 process. TSMC just release their latest roadmap, and says volume production of the N3 chips will start in 2H 2022. It remains to be seen whether Apple will continue to limit display support on the M3.]