The converse is true. If you have a FF account you are much less likely to be SSSS'd, even on one-way, last minute tickets. Who knows why, but it is true. Maybe it is because they can see that I have a pattern historically of buying last minute, one-way tix, so that is no longer a red flag, or maybe it is something else, but it definitely helps.

I would also agree with the observation that there are a number of one-way tix being purchased, especially since many more routes are priced as one-way trips instead of r/t these days.