Quick Answer
If a school is listed as requiring AAMC PREview, treat the exam as part of your application-completion checklist for that school. AAMC describes required participation as a category where schools may not consider an application complete until a PREview score has been received.
That is different from a school that recommends AAMC PREview. A recommending school may allow applicants to submit with or without a score. It is also different from a school that requires a situational judgment test, where a PREview score may satisfy that SJT requirement, and from a school exploring PREview for future use, where scores may be viewed for research or evaluation but not used to evaluate applicants in the current year.
Because those categories have different consequences, do not rely on memory, screenshots, forum lists, or an old spreadsheet. Confirm your school list directly before you choose a test window and again before major application milestones.