Far be it from me to defend Comcast, but it's not equivalent in the slightest. Comcast creates a separate network, with a separate IP, using their cable modem and the DOCSIS bandwidth available on their network. Its third-party usage does not count against your data cap, and any nefarious usage would not be associated with your own account and possibly subject you to civil or criminal sanctions.
Devices can only talk to specific Amazon APIs (which then hand the request to manufacturer APIs) with Sidewalk, they don't get to arbitrarily use your internet connection either.
