I agree that the distinction between neologisms and overloading existing words is an important one (and your examples are good!) - but I think the ordinary understanding of "jargon" covers both.

If someone announces "I'm going to stop using jargon!", and goes on to say things like "steel man", "shut up and multiply", "dark arts", then most people will agree he failed. The list of LessWrong Jargon contains plenty of non-neologisms like that.

Neologisms are a bit more obvious, but even the distinction between somewhat rare words (like "neologism") and specialized jargon (like "overloading") is pretty fuzzy.