Perhaps I have misunderstood some of the comments. But, I don't think many instructors are 'teaching' students to put their mask on their forehead to indicate distress. Rather, many actively discourage students from putting their mask on their forehead, EVER - not on the surface, not on the pool deck, not on land. If you don't want it on you face on land, drop it around your neck, or put it on backwards.I really don't understand all of this. . . . When I reach shore / climb aboard the boat, I push it up. Around my neck is uncomfortable, and I have no desire to "get used to it". The whole MOF thing is a crock IMO. Instructors who are teaching this should be instead telling their students to just keep their masks on in the water.
As for dropping it down around the neck, that is a developed skill, and a useful one. You are free to use it or not, as you choose. I teach that, actively. The mask is far more secure down around the neck than on the forehead. However, that is not being taught as the primary mask action on the surface. Instead, I teach divers to keep their mask on their face in the water, and drop it when they exit the water.
I was shore diving in Bonaire last week and routinely kept my mask on until I had walked out of the water, at which time I dropped my mask, so I could better see to navigate the coral on the way back to the truck. Much more secure there than on my forehead. Different strokes.