There are definitely errors.

BSD man pages tend to be good about attribution, e.g. https://man.freebsd.org/cgi/man.cgi?query=cat —

    HISTORY
       A cat utility appeared in Version 1 AT&T UNIX.  Dennis Ritchie designed
       and wrote the first man page.  It appears to have been for cat.

Otherwise, you go to the TUHS wiki for earlier system man pages.