Self arrest and pons is all about conditions. Enough said. Knowing when.
If very soft snow and you are wearing pons then the ONLY way to stop is by using your feet as your adze end of ice axe won't stop you. The problem lies when there is an ice layer under said slush. You can't predict this. OF course the only real reason you still have said pons on is because there IS said ice layer under that foot of slush. Or were too lazy to pull them off and like balling up snow under your foot making you slip that is... Not that we all haven't done this...
If on hard snow or ice, if your ice axe won't stop you, then your pons won't either. Even if you can use them, you can, the amount of weight on said pons better be VERY minimal. In such conditions need to learn to get ALL of your weight on the axe head, not possible, but "close". This takes upper body strength. Many don't know how to do this as they have never practiced on a steep enough slope. Essentially you have to do a pull up and "hunch" on your ice axe. This still leave significant weight on your knees/feet. Yes, in this instance using a Tiny bit of pon point pressure may help. It is certainly NOT the first option.
Different conditions-->>> Different methods.
PRACTICE! Practice! PRACTICE! Most broken ankle folks are due IMO due to folks who never practiced or thought about such situations ahead of time which is the same thing. There are a rare few who during said descent got bounced around so much that their pons hit without them doing it. OF course this probably means they were out to lunch when they slipped in the first place thus it was their attention to what the Hell they were supposed to be doing that resulted in the slip in the first place.
Bah, wrote too much.