In Stossel v Facebook et al (US District Court, Northern California), Meta/Facebook filed a document on 29 November 2021 stating:
...Stossel’s claims focus on the fact-check articles
written by Climate Feedback, not the labels affixed through the Facebook platform. The labels themselves are neither false nor defamatory; to the contrary, they constitute protected opinion.
The document was signed by Sonal N. Mehta signing as "Attorney for Defendant Meta Platforms, Inc."
So in the court filing Ms. Mehta is expressing that the labels “Altered”, “Missing Context”, “False”, and “Partly False” are opinion. She is not stating that the explanations of why the labels are given is purely opinion.
(alternative source for the court filing document)