I've kind of understood "dealer" to be someone who sells illegal drugs, and "budtender" to be someone who works the counter at a legal dispensary. I dunno for sure, I don't actually encounter these concepts often.

It does seem kind of silly, I mean we already have words that describe people who work in stores. On the other hand, it's specific and easily understood from the first hearing.

A dealer is Packer and a budtender is Dwight.

And “nano” isn’t a size; nano is a unit prefix.

Even the earth is smaller than 1 nano parsec.

Thank you for the pointless pedantry

Pedantic. When people say micro-scale/nano-scale they mean "measured in micrometers/nanometers". So a nanoparticle is a particle with a size that makes nanometers the most convenient unit.