So without having looked into it really, my assumption is that these podcast hosts will serve a specific file based on the response to an API call. If my Pihole blocks that call, they don’t want to serve nothing, so they fallback to a file that sometimes has “generic” ads (often for US-based companies) or other times no ads at all. Of course this doesn’t work for all podcasts, and as mentioned sometimes still has ads anyway. One day I might look more closely into it.