There’s a lot of assumptions in your question. Purely mechanical tricks usually don’t hold up to close examination. Throwing in some forms of misdirection and technique will make the trick look very different from what actually happens.
Well, yeah; that’s what I was alluding to with the quick mention of “a sleight-of-hand expert”: that I’d be unable to convincingly manage the effect if you handed me a mechanical prop like that — but that, if you give him enough time to practice with it, he’ll fool people up close and on camera while drawing attention away from the crucial stuff and getting everyone to focus on an irrelevancy or two.
One of two methods that I suspected was behind this trick is explained here. Balls in half shells. It even explains, indirectly, how he managed to bounce two whole, heavy white balls. I noticed the shrunken white ball right away in the original video.
Why this would fool P&T is beyond me.
He did it very well and they didn’t get to review it in close up slo-mo. They probably assumed shells were involved but there was enough complication that maybe they weren’t sure if they caught every technique.
But P&T will often offer a guess as to the trick. They have to use coded language and such so as to not reveal it to the public but they could have tossed out a word or two that magicians know.
That they didn’t guess at all is weird.
They are inconsistent. Sometimes they seem to like an act so much they don’t guess. And sometimes if they don’t know how one small part is done they’ll say they were fooled. It’s their show, they can do what they want.
The explanation at the end of this act may explain why they didn’t guess about Javi Rufo’s performance.