To be honest, the same applies when a developer gets promoted to team lead. I made this experience on my own that I no longer got in touch with the code written. Reasons are slightly different (for me it was a lack of time and documentation)

I am a scientist who rarely collaborates (unlike programmers and unlike most scientists).

When I wrote a paper in collaboration some time ago, it felt very weird to have large parts of the paper that I had superficial knowledge of (incidentally, I had retyped everything my co-author did, but in my own notation) but no profound knowledge of how it was obtained, of the difficulties encountered. I guess this is how people who started vibe coding must feel.