Essencialmente, você encontrou os sinalizadores de compatibilidade com versões anteriores (que, para ser honesto, eu nunca soube que existiam.)
Da página do manual:
SEE ALSO
The full documentation for head is maintained as a Texinfo manual. If the info and head programs
are properly installed at your site, the command
info coreutils 'head invocation'
Na parte inferior da página info coreutils:
For compatibility 'head' also supports an obsolete option syntax
'-COUNTOPTIONS', which is recognized only if it is specified first.
COUNT is a decimal number optionally followed by a size letter ('b',
'k', 'm') as in '-c', or 'l' to mean count by lines, or other option
letters ('cqv'). Scripts intended for standard hosts should use '-c
COUNT' or '-n COUNT' instead. If your script must also run on hosts
that support only the obsolete syntax, it is usually simpler to avoid
'head', e.g., by using 'sed 5q' instead of 'head -5'.
An exit status of zero indicates success, and a nonzero value indicates failure.