[naasking]

An opinion is a particular subject's belief [1]. That's literally the definition. "X believes Y at time T", is a fully specified fact and completely follows from the definitions of all terms involved.

[1] a view, judgment, or appraisal formed in the mind about a particular matter, https://www.merriam-webster.com/dictionary/opinion

[BugsJustFindMe]

None of that has anything to do with whether opinions can ever be considered facts. X believes Y at T is not the same as Y at T, and a statement about an opinion is not the opinion itself. Anyway, we're going in circles now and that's uninteresting to me.