> What did I get wrong there?

Nothing; you just missed some other considerations. For instance, Linux generally follows POSIX. That's what the 2004 version has to say about chdir's errors:

    ERRORS
    The chdir() function shall fail if:

    ...
    [ENAMETOOLONG]
        The length of the path argument exceeds {PATH_MAX} or a pathname component is longer than {NAME_MAX}.
    ...

    The chdir() function may fail if:
    ...
    [ENAMETOOLONG]
        As a result of encountering a symbolic link in resolution of the path argument, the length of the substituted pathname string exceeded {PATH_MAX}.

However, the following versions of POSIX moved the "length of the path argument exceeds {PATH_MAX}" into the "optional error" part.