Not 100% true. When I shoulder a steel butt-plate shotgun if it touches clothing it just slides. When using my rubber butt-plate shotgun it can stick to the clothes messing up the process and can legitimately slow me.
OP personally I actually prefer steel butt-plates. Recoil doesn't bother me even in rifles which people constantly complain about (Mosin Nagants, M95 carbines in 8x56r etc.) and I find it less comfortable to try and shoulder the rubber recoil pads because they aren't designed to be shouldered properly, rather to go everywhere so someone doesn't get hurt (which I also believe has made a generation of shooter who don't know how to properly shoulder a rifle). To each there own.
.If it's sticking, you are doing it wrong. Raise rifle, jam back into shoulder. Don't drag it into place.
There are some rifle pads that are a bit unnecessarily sticky though, no question about it. Again, the way around it is to lift it up, then plant it back.