That particular, possibly nitpicky part of Han's backstory

It's not a big deal. I just don't like it. It reminds me of GOT and Jon Snow. I don't like this too. But it may actually explain the name Kylo Ren even further. He invented it or he was given the name like his father once did.

 

Hey, great minds think alike

 

Found this bit while cleaning out bookshelves last night. It's from the 1983 Return of the Jedi storybook I bought in 5th grade before the movie's release. Yes, good ol Lucasarts or whoever released the entire story before the movie.

 

When I was at school, the headmaster mispronounced my surname. Out of personal privacy, I'll just leave out what my surname is and what it was mispronounced to.
Over time however, that was eventually shortened to a nickname by the 'cool' kids to just 'Skins'. I hated it because it's what the guys I hated at school called me.

After I left school however, I somehow kept the nickname and even asked new friends to call me it. They made assumptions it was because I always had 'skins' available for their weed. My irritating school nickname due to the head stumbling on his words because a cool nickname (even though it wasn't true) to those who had never known me.

That was a long time ago and only a couple of guys from my past call me that now, but I took a negative nickname and made it my own so that I was in control of it. I don't see anything unrealistic about Han doing the same via the Empire that day.

 

We're also making assumptions about how surnames 'work' in the Star Wars galaxy. Or rather how they work amongst the many many cultures of the Star Wars galaxy.

Even here on Earth in the real world, surnames have not always been a thing and the way they are used and applied is different for different cultures - and some don't even use them at all. Just because surnames are common in many English speaking western parts of the world, doesn't mean that's how it is everywhere.

So maybe Han never had a surname - because maybe his father never had a surname either. Perhaps it just doesn't work like that on Corellia, or at least amongst the lower class citizens.

It could be his father was called Denker Shipbuilder, because he worked building ships. Or some other kind of naming system that isn't passed down to offspring. Han isn't Han Shipbuilder because he didn't follow his father into that trade.

Could be that on Corellia any last name is a more like a clan name - and if you're not in the clan anymore, you don't use the name anymore. You become part of another clan, and take on that name. Or you go it alone and don't take one on at all. Like Han does.

The Empire on the other hand want to impose their way of thinking on all cultures, so insist on last names to join their ranks.

Anyway, there are any number of reasons Han didn't have a last name up until that point - many of those reasons being that last names might just not apply in the way we think of them applying in our culture.

But presence of a surname doesn't have to be synonymous with a family name. Well, maybe at least until you marry a member of royalty!

(Denker is just a name I made up by the way. I have no special insider information )