it sends a message

Yeah, I think in the movie the “knobs” were actually handle types. I don’t think they would have had the leverage to turn knobs without thumbs.

Edit: this site claims that the wrist twisting motion would have been difficult for raptors to do due to the natural orientation of their claws:

https://dino-world.com/could-a-velociraptor-open-a-door-5-17670/

Lever-style handles would theoretically be easier for a Velociraptor to manipulate than round knobs. The downward pressure required aligns better with their natural claw-gripping motion. Round knobs would require a twisting motion that might prove more difficult given their hand orientation.

They’re like birds, right? Don’t they have a cloaca instead?

searches

Apparently yes, though this author couldn’t resist “butthole”…

https://www.livescience.com/first-dinosaur-butthole-found.html

1st preserved dinosaur butthole is ‘perfect’ and ‘unique,’ paleontologist says

This was a multipurpose hole.

The first dinosaur butthole ever discovered is shedding light where the sun don’t shine. The discovery reveals how dinosaurs used this multipurpose opening — scientifically known as a cloacal vent — for pooping, peeing, breeding and egg laying.

Why is it raptor-specific?

For the Jurassic Park reference, probably