While it may have been a “joke”, there may be some merit to this. It probably isn’t as good as some port knocking strategies, by itself, but maybe a useful technique as part of some of the more traditional strategies.
I think I would prefer a time based one time port number algorithm to port knocking, as a way of obfuscating which port ssh is listening on.
Yeah, for sure. I just don’t know how this compares to, say, an implementation which uses an encrypted token or something. The encrypted token knocking strategy feels safer than TOTP, but maybe they are about equivalent–I don’t know all the details.