Favorites are set by you, not Sonos. If you have something that you shouldn’t think should be there, ‘edit’ to delete it. 

I am well aware that I add Favorites and not Sonos. That was not my question.

When I add a Podcast to Sonos Favorites sometimes the Podcast shows up under Podcasts and sometimes a Podcast shows up under Albums, Sonos does not give me a choice of where to put the Podcast, Sonos makes the decision to put a Podcast under Podcasts or Albums.

Ah, I misunderstood. That does seem odd. Have you called Sonos Support directly to give them examples, and see what they say?