When a participant registers and answers PII questions, and their answers are aggregated after 90 days (or shorter if changing ttl to test on local), and the participant cancels their registration, and the participant re-registers, then the participant should not be shown the participant questions or be able to re answer them.
This can be reproduced on the event page, in Special:RegisterForEvent, and via the API (answers are not rejected).
Chrome, local env, mediawiki 1.43.0-alpha
This is what is happening currently: