The upside of IANA doing it would be a standardised place for sites to move to. Without coordination, different sites would move to different TLDs, probably mostly based on what isn’t already registered. IANA could create a new TLD for this and give existing whatever.io owners a chance to register whatever.iox before its generally available

How exactly is it hashed? There aren’t that many possible phone numbers, so it might be viable to just try every valid number until you find one that matches

Blaming Spotify for this is like blaming the company that made your TV for showing you ads that are part of the broadcast. Unless Spotify makes the specific podcast you’re listening to, they’re just playing you the content someone else made, including the ads they included in that content.