The commercial reason to add it is the richer search result it can earn, so the types worth implementing are exactly the ones that still produce one. That list changes, which is why the rule in our catalog carries the condition that would make it stale.
Google stopped showing FAQ rich results for most sites, so FAQPage markup no longer earns a listing change. It remains reasonable as a description of the page; it is no longer a reason to do the work.
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