Those words, about it being "easy" to change the port, are a bit misleading. They refer to a permanent relocation of the port, not something which is end-user configurable.
So, in practice, the port cannot be changed (for that, we would have to rebuild the entire license library).
However, I don't really see any reason why the port would need to be changed; if you are behind a firewall you need to open the port, but the procedure for that is independent of the port number. The only case where it might be relevant is if two Sentinel license servers use the same port, but in that case they can also share the license file.
In FLEXlm this is different since there is also the vendor daemon, and because license servers from different vendors cannot cooperate.