I would say it's less overhead than downloading the entire db to query it locally...? What is your suggestion for accessing a static database with less overhead?
You're referring to the CPE which is owned and managed by the ISP just as they own and manage other routers in their network.
The other person said that they can push firmware to private modems though, which is not possible without that modem being configured to accept such pushes.
Perhaps you're thinking of CWMP (TR-069) which is a protocol that ISPs often use to push configs to modems configured to receive them, but again, it cannot be used to arbitrarily flash the firmware of private modems.
I'm not sure how you think those ISPs supposedly push firmware to private 'modems' of all shapes and sizes, but I would like to know because I had a hell of a time reflashing my router with OpenWRT.
Just curious: What do you presume that NSA would do to prevent a multibillion dollar private company from pursuing a communications satellite constellation along all the correct legal and licensing channels?