Except that happens often in my games, or like you call it yourself, all the time.
People don’t have same experiences as you do, but you somehow fail to realize this.
You can bomb bases with them and higher up jets become multi purpose so your argument is pretty moot.
Also, you failed to realize that playing Air modes at peak efficiency requires you to only research Air branch, nothing else is even relevant.
I would stop viewing it as a tank mode if tank mode was present, but that’s not the case and currently only mode where you can spawn a tank is Ground Battles.
So yeah, in order to reach peak efficiency in this mode, you’ll need to grind through Ground, Air and Helicopter branches, but people playing this mode still get same RP/SL gains as people only interested in Air Battles and aren’t required to research into any other branch.