Clearly there are more parameters than accumulated practice time, but I'm really getting at the point that some people (most people?) probably could manage to reach many of those tricky shots given enough practice. But they don't try every time and so sell themselves short in the long run.

Rafa had to start somewhere, and he definitely did not hit every shot when he was a young boy.

Tying this back to the OP - my criticism of the 'Umeshisms' described are that they're absurd when applied to a system where your strategy has fixed outcome probabilities. If you could improve your ability to get through airports quickly with practice, then it would be self evident that missing the odd flight is a consequence of improving your skill at the optimum rate.

Or maybe I just don't understand the frame of reference of the OP.