When the impossible goal is to solve a 10x hard problem in 1x time live during an oral exam, no. But it did have a filter effect, so that the Jewish students who did pass the entrance test were much higher ability than their average peers.
I doubt it. Those problems are close to impossible to solve for ordinary students, therefore many talented but not necessarily genius students lost the opportunity to get good education. I'm a firm believer that students need to be pushed to stay in their discomfort zone, but Jewish Problems can easily push most students into panic zone.
That's one of the principles of deliberate practice: go just beyond the comfort zone, in the area where you feel a challenge, but an approachable one.
The point of the Jewish Problems is that:
1. They're an entrance exam. They were explicitly designed to discriminiate against otherwise worthy candidates.
2. The key feature of the problems is that they are not difficult because they are an average example of a difficult branch of math. Instead they are easy problems, but they are only easy if you can figure out the correct substitution. Otherwise, they are extremely difficult. In other words, getting good at the problems won't make you a better mathematician, it'll just make you better at passing that particular test.
It happened in music a few times.. people invented techniques and subgenres because they tried impossible things or had below useful instruments.