For example: When I leave my home to walk to the shops or something, I will often put YouTube on and listen to something, when I get to the top of the road and the phone can still see the WiFi network but can't use it reliably playback will often stop before it has chance to to fully swap to cellular (And Background Play on iOS YouTube often will need a kick to start playing again after a network error).

So I have got into the habbit of "turning off" WiFi via control center as I'm setting up what to listen to as I'm leaving the house and the playback pause issue is gone. With the current behaviour of control center it will "re-enable" WiFi by the time I get home so I don't forget to swap back to WiFi and eat up my cell data.

EDIT: When I want to turn WiFi completely off, I have a shortcut to do just that which I added to to the Assistive Touch menu.

Not in this case. The person who drills down into his settings to REALLY turn something off really wants to turn it off. So Apple should respect that, and treat the control-panel on/off as persistent in that case.

That would serve everyone's preferences and reasons: People who only turn the stuff off from the control panel would get the temporary behavior of those controls. People who turn them off at the system level would get the persistent behavior.