I see what you're saying, but I think you're taking the analogy more literal than I meant it! The "nozzle" isn't the SIM card; the "nozzle" is CDMA, or the CDMA hardware.
CDMA is a component in the "gas."
Radio is the engine and needs to be tuned for the gas (signal) so it can burn it (use it compatibly).
Signal is the gas that runs the service.
The SIM is the nozzle through with the service (or gas) flows into the (engine) radio.
As you have pointed out, if one has a valid SIM and inserts into a device with a capable radio it will work. But what if I don't have a valid SIM that I've used on an approved device? The SIM fits, but does nothing correct? Can I walk into the Verizon store and activate a device that isn't "approved" just by purchasing a plan and getting a SIM?
You are outlining a workaround and an exception (iPhone), not IMHO a real BYOD plan that asks only will the nozzle (SIM) fit and can the engine (radio) use the gas (signal)?
So you are tricking the "nozzle" (SIM) by inserting it into a preapproved "fuel intake" (SIM slot) of a "car" (phone) with an "engine" (radio) that is already approved... Let's go back to JimmyGas (Verizon)...
Tommy pulls into JimmyGas in a Ford Escort that
is in the JimmyGas database, puts the nozzle in the filler tube and bing-bong the pump is activated. He pulls forward and his confederate pulls up to the same pump and fuels up a Chevrolet Impala that
isn't in the JimmyGas database by using the preactivated nozzle. Later on, Steve pulls into JimmyGas and he has never been there before. The pump doesn't work. But Steve goes inside and the attendant tells him, "Hey, you have a Ferarri. We honor all Ferraris here, let me just put your VIN in our system." Steve then pumps his gas and races off. Poor Tammy pulls in with a Chevrolet Impala that is the same as the one Tommy tricked JimmyGas into fueling and she can't get the pump to work. The attendant tells her, "Your car maker has to give us all the VIN numbers so our nozzle will recognize you car." Tammy leaves without getting gas because she isn't a customer already and has no access to the trick Tommy used...
Meanwhile, over at Pedro'sPetrol they are just letting people drive up and pump unleaded into any car that runs it. There is no database check before your fuel will flow...
In my analogy CDMA is not the nozzle. That doesn't quite fit. It's more like a fuel additive or ethanol.
The restriction isn't "under the gas cap" it is at the "nozzle" and is ostensibly to ensure that the "engine" can consume the "fuel" and the database becomes an extra hindrance for those that want to build a car capable of using the "fuel." It's an extra step that doesn't need to be there. It may be to "protect" the consumer on the surface so that they don't accidentally try to use a device that won't work, but the reality is that it hampers consumer choice and freedom. Where the analogy breaks down is that if you run the wrong fuel in a vehicle it damages the engine. If you put an incompatible SIM in a phone it just doesn't work. It won't damage the device.
No one is suggesting that Verizon has to supply signal to devices not capable of receiving their signal, but there is no parallel in GSM based carriers. If the Sim fits and the signal can be accessed you just do it and go. No workaround, no asking to have an IMEI approved before you connect.
It should be no big deal as the Verizon SIM isn't going to damage a phone without the right radio. No harm no foul, yet they act like the database measure is there to protect the consumer. It isn't. It's only there to preserve their model of selling branded phones.
There is a restriction somewhere... I just don't think all OEMs are interested in complying with what the restrictor asks to have it lifted. I guess some would blame them, but I can't. Those that do blame the OEM seem to be the ones using the restrictive system.