Registering to specific occurrence of meeting

I’m working with the “add registrant to meeting” API and specified occurrence in the requset. however, when i get the registration email, i see im registered for all occurrence.
when i query occurrences i see my registrant every time. Also last_name is required when I register with a specified occurrence. This shouldn’t be the case as the API docs say registration only requires first_name + email

POST /v2/meetings/{my meeting}/registrants?occurrence_ids=[one of the occurrences]

body: {
first_name: “test”,
email: “
when calling this, it asks for last name even though registering without occurrence doesn’t require it and the api docs don’t say last name is required

Then when calling GET /v2/meetings/{my meeting}/registrants?occurrence_id={another occurrence, not the one i registered for}

I see my registrant, even though they did not register for that occurrence.