There have always been updates that only apply to certain newer devices, not just recently. iOS 4 only gave home screen wallpapers and multitasking to 3rd and 4th gen iPod touches and iPhones, but the 2nd gens got iOS 4.
I expect we'll see additional features in 15.2 that are for both platforms (aside from Apple Intelligence), but we'll have to see. A .1 update isn't that big usually (and a lot of .4 or .5 updates in recent years were essentially "Bug fixes, oh and we added 1 minor feature in Podcasts" or something) anyway.