@srlawren wrote:... the Apple Watch 3 LTE does not have a SIM card slot in which anyone could put their PM sim to test it. Instead, the watch uses an "eSIM", which is built into the device. That's the crux of the issue, that PM does not yet support eSIMs.
Good catch @srlawren!
Apple says "... introducing a built-in eSIM that is over one-hundredth the size of a traditional SIM card, making over-the-air activation possible without compromising space."
"eSIM" means "embedded SIM" ... it still has all the functions (circuitry) of a SIM card but it's built-in, integrated, permanent. The GSMA is trying to promote eSIM with emphasis on end-user advantages:
"The information on it will be compliant or rewritable by all operators, meaning a user can decide to change operator with a simple phone call. A new SIM will not be required, nor should there be any time delay in switching the eSIM to its new purpose. There will also be no physical swapping over required by the user."
Although the real appeal is to device manufacturers. It's reduced to a tiny bit of silicon, it doesn't even have to be a discrete part on the mainboard if it's integrated within a larger SoC. Don't need the physical bulk of a SIM card, or the slot/tray which holds it, or any of the electrical interface components.
And full, exclusive control over SIM cards has great appeal to device operators. For obvious reasons. In practice, eSIMs can effectively be used as the new way to "carrier lock" devices - I doubt that switching carriers will only require "a simple phone call", at least not before some CRTC-mandated regulations are written to explicitly require it.
