Did Han know what a parsec was?

If you've seen the original Star Wars you may recall the (in)famous line where Han Solo boasts about the speed of the Millenium Falcon:

Han Solo: Han Solo. I'm captain of the Millennium Falcon. Chewie here tells me you're lookin' for passage to the Alderaan system? 
Obi-Wan: Yes indeed, if it's a fast ship. 
Han Solo: Fast ship? You've never heard of the Millennium Falcon? 
Obi-Wan: Should I have? 
Han Solo: It's the ship that made the Kessel Run in less than twelve parsecs. I've outrun Imperial starships. Not the local bulk cruisers mind you, I'm talking about the big Corellian ships now. She's fast enough for you old man.

Now, it doesn't take much of a physicist to tell you that a parsec is a measurement not of time, but of distance. A light year is a distance measured as the distance light can travel in one year. A parsec is approximately 3.26 light years (that's around 19 trillion miles). So is Han being dense?

Well, the Star Wars Expanded Universe writers concluded not, and developed an explanation where the Kessel Run is a smuggler's route from the mining planet of Kessel that skirts a cluster of black holes called the Maw. The faster the ship, the closer you can skirt to the Maw, and therefore the shorter the distance, hence parsecs. This explanation quickly became canonical and until recently I assumed it was correct.

Until I read Darths & Droids a few days ago. If you haven't seen it, it's an excellent webcomic that imagines a world where Star Wars exists as nothing more than a D&D-style game master's imagination, and the events of the movies are reinterpreted as the actions of a group of role-playing friends. According to the annotation on this one, in the original script, Obi-Wan was supposed to treat Han's claim with derision, as it showed he didn't know what he was talking about.

It really was just a heap of junk after all. Who knew? Source.

Apparently a minor change, but when you think about it, it makes a big difference to the character. He's always portrayed as a slightly reckless but fundamentally competent character, whilst the Falcon was not much to look at but was genuinely fast. Yet in the original script, Han started out as a bit of an idiot (although he's clearly supposed to have matured by the Empire Strikes Back), and perhaps the Falcon was really no more than a heap of junk without even speed as a redeeming feature.

Crazy stuff. I'm not going to lie, my world was temporarily rocked. It rather changes the interpretation put on it by just about every content creator since, simply because Alec Guinness didn't portray quite enough derision.