Thanks for reaching out about this here in the Community. We'll be happy to explain a bit more about this.
Spotify doesn’t play or include ads that interrupt the listening experience of Premium subscribers. However, some podcast creators may include third-party advertising, host-read endorsements, or sponsorship messages in their episodes.
Spotify gives the podcast hosts the option to choose if they would like to have a dynamic ad slot in their podcast, but that isn't something Spotify can control - it's up to the individual podcast owners if they choose to have that type of ad in their content.
We hope this sheds some light on this. If you need anything else, give us a shout.