Eh, if they're that capable, they probably have a lot of room to optimize for whatever they want. Maybe they consider rivets ugly—or consider making such a thing without rivets to be a demonstration of their skill (which it would be). I'd agree you can't assume for certain they wouldn't use rivets, but I'd say it seems likely they wouldn't.

(Of course, the chance they'd choose to make rivets in an exact shape and size and style that is presumably mass-produced somewhere on Earth is very unlikely unless they wanted to make something to blend in.)