Quote Originally Posted by Trzeci_Wymiar
I'm sure "dialect" could be used loosely to subsume argots, it's a very generalized term that has no real meaning at the level of the nitty gritty other than "variant."

Mirriam Webster, in fact, shows as its second definition for dialect: "The language peculiar to the members of a group, especially in an occupation; jargon: the dialect of science."

Argots, jargons, dialects, they can be used synonymously.

So it's not a HUGE mistake, in fact it's not really a mistake at all.
Remember that terminology may vary and be very different in different languages. You are right that "dialect," as a matter of fact, is used loosely. The reason is that it is very difficult to differentiate between languages and dialects, dialects and other subdivisions... That is why, I think, it is more "politically correct" to use the term "lect" in many cases. In Russian linguistic tradition, you can't apply "dialect" to argots and jargons. Actually, argots and jargons even tend to be separate phenomena, and thus we have three different but "loosely" understood "speaks". I must say that there is no agreed standard as to what one might call "dialect. Period" when studying variations of the Russian language. Govori and narechiya are more understandable somehow. And, last but not least, jargons and argots are not included in them because they have specific usage within language.