Today Pro Tools uses OS X .midnam files for naming patches for external MIDI devices. However, today there's more common to use software instruments than external MIDI devices so we need a way to handle patch names for software instruments.
There is a workaround to use these files for software instruments, but then you have to create fake devices and connect them to a real midi device. And then you must choose both the fake midi device and the software plugin as MIDI Output Selectors. This could be easier!
Then this "old" way to naming patches isn't portable. If I use the workaround above and then save and send my session to a friend that have the same software instrument he will not se the patch names because they are system dependent. For software instruments the patch naming should be session based rather than system based.