I've also submitted a feedback report for this issue (FB13208693).

There was an error in my code snippet after all. I didn't realize that price points have unique identifiers for each country. My request used USA as the base territory but included a price point identifier (eyJz...) from a different country. To avoid this mistake, set a territory filter when querying the available price points for an in-app purchase.

This bug is still not fixed in Xcode 14.2 (14C18).