Looking at the Episode extras data policies, we have two slightly different definitions for appearance (emphasis mine):
A Cast Appearance can be used to indicate which of the show's Main Cast members actually appeared in the episode.
A Crew Appearance can be used to indicate which of the show's Main Crew members were actually credited in the episode.
The way I enter cast appearance is straight from the onscreen cast credits. That is however not always the same as an actual appearance. For various reasons some shows credit cast even if they did not actually appear. One current example is Star Trek: Prodigy.
So should Cast Appearance be interpreted as "This cast member has contributed their talent to this episode"? Or go with "They are credited for this episode", just like we do for the Crew Appearance?
My preference is going for credited in both cases. For one thing, that is much easier to double-check. And prevents discussions about cast appearing in footage from previous episodes for flash-backs, and things like that.
You could also allow for exceptions or enhancements with new flags to show "Credited but did not appear" or "Appeared but was not credited".