That would also be equally untrue.
There are many types of ISO files, and all Ubuntu and flavor of Ubuntu ISOs will work with the procedure outlined here, along with any other distro that uses the same type of ISO file.
If a person wants to write a non-Ubuntu ISO I would expect them to use the procedure that matches the type of ISO they downloaded, which they’ll get from the web site where they got their ISO.
The procedure documented here works for any Ubuntu, or any flavor of Ubuntu such as those found at https://ubuntu.com/download/flavours (ignoring any bugs/issues with development daily ISOs)