I see your point and thought about it. Yes along the lines of a faster car means a bad driver can drive faster the shaft will certainly help average players do some things better assuming the claims are true.
My point was as you pointed out that an increase in equipment performance benefits the pro more because of decreased situations where the equipment was at fault for the miss. (in so much as equipment could even be the cause.)
Aside from situations like a miscue from a glazed tip or the tip popping off (or a gaffed cue with say lead weight at the tip), I don't see how the cue is ever the cause of the miss (this is not the case for balls skidding (a "kick") or bad table rolls, which are the fault of equipment). I say this because the cue ball will react as it should given the cue, and a player can always adjust to it. Of course, one possible advantage to LD cues is that the player has to adjust less.
The point I was making was slightly different than your point about the equipment causing the miss - I think the test is whether a cue can be forgiving of mistakes, like a larger sweet spot on a golf club.
Gideon