Telnet support for PTT has already been deprecated for security reason so I am not sure PTT still count as a telnet-based BBS. Only ssh and websocket is supported nowadays.
Consider that the GNU version of "fgrep" was "deprecated" for just under 14 years. And yet people were very clearly still using it in 2022 (when the 2021 code change apparently hit Debian) and 2023 (when the change hit Chris Siebennmann).