Am I the only one mildly surprised but not bothered by this implementation choice?

Sure, making a true circular list is easy enough both computationally and code-wise. Nevertheless, it's still something "weird" and "unusual", yet another thing that has to be tested and understood and debugged. A linear list is on the happy path, and the difference isn't going to matter for anyone in the real world.

I'd personally have made it circular anyway just for the sake of my inner sense of correctness, but making it linear and finite is, IMHO, a defensible engineering choice.