Is that a good thing? I think getting stuck is an intrinsic part of the learning process and sometimes it's good that there isn't an immediate answer from a senior. For some things you'd never have solved yourself, sure. But pain and suffering is a big and important chunk of learning and I fear we just throw it all out of the window with asking AI.

I am skeptical. This is a testable hypothesis, and I know there have been tons of research done trying to provide evidence of claims like these. However I have yet to see a convincing evidence. If this statement was indeed true, I think experimental data backing it up would be old news at this point, it however is not, and I suspect that is because junior developers are by and large in fact not learning faster or more with the help of AI.