OP is arguing that there are many ways of communicating in a language, including slang and various registers and dialects, and just because you and I don’t understand all of them that’s OK. They’re still valid communication and not the same as stunted linguistic or communicative ability as the ability to communicate between people familiar with the slang or dialect is not stunted at all.
No, OP isn’t arguing that.
OP is arguing that there are many ways of communicating in a language, including slang and various registers and dialects, and just because you and I don’t understand all of them that’s OK. They’re still valid communication and not the same as stunted linguistic or communicative ability as the ability to communicate between people familiar with the slang or dialect is not stunted at all.