Ok sure, but that's not likely to have anything to do with app store pricing etc. That's just GCP trying to acquire customers. They're not going to start trying to punish customers for other decisions because that would be an incredibly way to shoot yourself in the foot. This is a problem AWS already sees a lot.

Smaller companies who partner with large companies like Google or Microsoft see these large co's as single entities and not through their sub-divisions. Spotify probably partners with Google in Ads, Android, Cloud areas at minimum. Spotify is already a publicly-known large GCP user. So they might be just playing their chips.