Seems like it's the Linux limitation[1][2]. Testing it myself, I made a directory "/home/bla/a", and inside this directory, a symlink that refers to "../a".
After 41 invocations of "cd a", doing another "cd a" takes me to the root directory (so /home/bla/a).
Perhaps when the web server tries to follow the 41st symlink the system says "You've recursed to much, go to /some/path/not/accessible/to/the/http/user" and that's why it returns a 403.
And the directory (well, symlink) isn't listed at depth 40 because the server knows following it will lead to a 403.
[1] https://lwn.net/Articles/650786/#:~:text=Linux%20imposes%20a....
[2] https://unix.stackexchange.com/questions/79571/symbolic-link...
