If a "harder" rubber feels softer, that's not a matter of quality. Hardness is a measurable, purely scientific metric, so if a 42d rubber is softer than a 41d, that means at least one of them is not correctly labeled.
I am convinced that Pro players care about two things in their rubber, compared to commercial options: consistency and ability to withstand some serious usage (and boosting).
Yes, a hard hitting Pro will want to use a harder sponge, but there's no reason to mislabel the hardness. In fact, for consistency, it makes sense to be sure that a 42d sponge really is 42d.
The consistency in their material makes sure they don't have to think about adjusting to their rubber during play, and instead can use their energy for more useful things like tactics, form, footwork etc.
