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.

As for Olya's point, yes, the central dialects are referred to as "govory," but the Northern and Southern dialects are referred to as "narechie," if that makes a difference.

As for the word "standard" it's fairly useless to try and use it seriously. Up and down linguistics there's debates as to whether "standards" even exist. The general consensus is that they don't. Standard dialects are dialects with the largest "armies and navies," they're chosen by the accident of history and/or the arbitrary calculations of legislators.

In fact, learners should be aware of the distinctions, however minor. To a Russian speaking to a Russian, dialect variations might only be considered in passing if at all, completely comprehensible. However, if a non-native starts using highly regionalized words in the wrong region and rather inconsistently, he'll probably be laughed at.

If I started interspersing tsokan'e (tsaj and tsysto as opposed to chai and chysto) and the fricatives "gh" and "h" for "g" and started saying "damno" as opposed to "davno" or "dobre" and "vyoda" along with muscovite speech, I'd probably be labeled as confused.

Just the same as if I had heard a Russian saying "Y'all" in a southern way with an admixture of New York features and majority-of-the-time California surfer's speak. It'd be weird - it'd benefit the learner to be aware of the variations so as to be able to be consistent. If you go to the southwest and start speaking like a Belorussian, stick with it, and don't try to mix it into the "standard" muscovite of the classroom.