It's still a science goof. A technobabble explanation by another writer YEARS AND YEARS after the fact doesn't change that the first writer didn't know what a parsec was.
Yeah, but it's pretty clear that Lucas did
know what a parsec was way back in 1977.
I guess that's not clear to me. It reads as though he misused a term and when someone called him on it, he shifted the blame by claiming the character was written to be foolish. Maybe that's not what happened, but that's how it reads from here. And it doesn't really ring true.
If he had claimed the character was written as trying to put one over on his customers, that would ring true to the character and I'd have believed him. As it is, I can't see it as anything other than writer error.