A recent nmap (>7.30, commit July 2016) will have a correctly formatted man page; https://github.com/nmap/nmap/issues/463
Most distros will properly have an older release packaged and won't bother updating just for the man page; https://bugs.launchpad.net/ubuntu/+source/nmap/+bug/1684304
Re: Is a port scan good enough?
Most distros will properly have an older release packaged and won't bother updating just for the man page; https://bugs.launchpad.net/ubuntu/+source/nmap/+bug/1684304
Mikkel