It removes the section at the bottom of the man page, and has this addition to the source code comments:

    +#ifdef USE_PAM
    +
    +   Actually, with PAM, su has nothing to do with whether or not a
    +   wheel group is enforced by su.  RMS tries to restrict your access
    +   to a su which implements the wheel group, but PAM considers that
    +   to be fascist, and gives the user/sysadmin the opportunity to
    +   enforce a wheel group by proper editing of /etc/pam.conf
    +
    +#endif