Got a link?

The only way I can think is the Google push service reading the channel id and dropping the push request.

Unsure if that's the case, but I remember having read from another situation that by contract, Google can tamper programs published on the Play Store if they wish. Perhaps that's the case?

Or maybe they could block channels if they pass through Google Play Services, or if these Services can monitor internet requests?

I do not know, but I would imagine Telegram needs to release a different APK with additional restrictions on Google Play in order to comply. Otherwise, google would simply take it down.