I just spent a couple of minutes trying to 3D touch to properly disable wifi, then googling how to do this with 3d touch and came up empty.

Either it doesn't work that way, or it's well hidden and appears not great in terms of UX.

Overall, I agree with you though. I'm personally not clear on the utility of turning off just wifi or just bluetooth. I assume (hope) airplane mode turns everything off. But in any other scenario you're still leaking location and other information.