I wont argue about the OTA server infrastructure, when I wrote my statement above I chose to say that to imply (and make strong contrast) that carriers (like ATT, Verizon, Sprint and T-Mobile in US, I was not arguing about the rest of the world) can only decide for their own variant. FCC is not pushing Samsung to wait what ATT, Verizon, Sprint or T-Mobile has to say about the SM-N950UZKAXAA device (or the OTA for SM-N950UZKAXAA). Now, what gets negotiated under closed doors when Samsung tries to launch new device (lets say what negotiations went when S8 was about to be launched) on a given carrier, that is everybody's guess. Verizon and ATT are so powerful that may negotiate some terms with Samsung that may affect updates. But these are things negotiated behind closed doors and are not a public knowledge.Technically no one gets its update from a carrier and no carrier has its own update server infrastructure. So technically is clearly wrong to say carriers provide the updates.
Second, for the non-branded versions (like my N910F) no carrier has any saying in when and how to release an update. It's Samsung to define, program, build and deploy the firmware.
Third, only for branded variants the carrier has a saying in how the firmware looks like, which addons have to be incorporated and they can test it, which may delay the publishing. But even then the build and final decision to publish is up to Samsung.
Having said this, it's absolutely clear that the lack of an update for N910F is only Samsungs fault. The carriers are not involved in any way.
The thing is that FCC is not forcing Samsung to wait Verizon, ATT, Sprint and T-Mobile to bless OTA for SM-N950UZKAXAA device. Technically, Samsung can do it whenever they feel like releasing OTA (given the OTA passes Google cert).
Now, what Samsung has agreed to behind closed doors .... ???