Pressure is pressure is pressure, so even though the HWH tank is large, pressure will still build up in it and work just fine.Also, you say no need to bypass the water heater with this method, but I'm wondering how well the air would go into the tank then through the out hose for your hot water lines. I question how much pressure would even be going through those? I guess you've done it enough times without any issues though, so clearly it works
FYI, Brad has the fancy shmancy air adpater - I never even knew they made one that nice! Another option... search for "Camco blow out plug".
Personally, I just like seeing that pink color come through everywhere so I know there are no pockets of water that gather somewhere. But air can certainly work.
Keep in mind, you'll still have to pour AF into all your drains, including a couple pours into the shower drain for your step-down pump to activate a few times. Also a couple flushes with the head.
If the marina winterizes your engine, pink may or may not push all the way through the HWH heating lines if they don't first drain the hoses.