I can't put words in his mouth, but RogerM may have been speaking of having obtained a level of "practical mastery" over the tabled faro. That means that it's a move that you feel comfortable using, just about anywhere, as long as you are in control of certain necessary elements. For instance, you might have practical mastery over an in-the-hands faro as long as you can choose a decent deck and make sure that it's a good one for faros. In this case, I'd say practical mastery could easily approach 95% accuracy or greater. In any case, that's certainly good enough to use under fire for paying audiences.
I consider myself to have achieved practical mastery over the second deal and bottom deal. That means I'm not afraid to use these moves for paying audiences (even very large or important audiences, like a national television spot). I'll pretty much use them anytime, anywhere as long as the deck of cards is one of my choosing. And I'm not worried about missing - my accuracy with these moves is well over 90%. That's practical mastery. But I'd never tell you that I can hit a bottom deal or a second deal 100% of the time. Nor have I ever seen anyone who can. Everyone misses from time to time, even in important situations and the misses increase in frequency as the difficulty of the move goes up.
Back to faros....
In the case of a tabled faro, you might demand a proper surface, such as a good close-up pad or similar surface and a deck that cooperates when shuffled from the bottom up. As we all know, a deck that's been cut the wrong way can be very difficult to table faro, regardless of how good your technique is. I think that if the bar you've set for yourself is "practical mastery" then these are reasonable demands to make. And I think you could achieve excellent results, perhaps even way above 90%, if you were able to control these elements. I think Martin Nash was above 95% accuracy when he had his cards on a good surface. That's practical mastery.
But it ain't "100% of the time."
If RogerM was talking about practical mastery then he and I don't disagree all that much. If he's going to insist on "100%" as literal truth, then he's going to look awfully silly, since I can line up 40 of the best card handlers in the world that will disagree with him yet he's not willing to provide any proof of his claim.