An interesting little detail. Any seasoned developer is likely going to take substantially longer if they have to use any IDE except their everyday one.
I've been using Vim/Neovim for over a decade. I'm sure if I wanted to use something like Cursor, it would take me at least a month before I can productive even a fraction of my usual.
I recently switched from vim (16 years) to vscode and perceived my productivity to be about the same after one week.
No objective measurements here; it might have even increased. But either way, "a month to regain a fraction of productivity" is extreme hyperbole, for me at least.