In some games I've noticed that I get +0/-0, which is sorta fine. I don't quite understand how it works though, mostly because in those games, there are often times people with higher PSR than me, who still earn points.
In the last game, we were 25%/75% (I was on the 25%) and people with higher PSR were earning points, but I wasn't. I know PSR really isn't like important compared to player stats like k/d/a, denies, and xp/minute, but its still a little odd.
*edit* Just tested it this game, if I swap from legion to hellbourne, I get points, but if I swap back to legion, I don't. So odd.