I'm in the eSIM business and the same QR code you can scan on an iPhone will work on a Pixel, Samsung and a few other eSIM supporting devices. You might be thinking of the Apple SIM, where Apple to work directly with those carriers.

What are you basing that assertion on? All the eSIMs I’ve ever used have come direct from the carrier, and in some cases those carriers have very small presence and aren’t know for being at the front of Apple queue for services.

Then there’s the dozens of companies in the App Store like https://www.dentwireless.com/ who all provide eSIMs for international travel. I find it hard to believe they all have agreements with Apple, it normally costs far to much to deal with Apple for bottom dollar companies to make any money.

There are various threads on their developer forums alluding to it, eg. https://developer.apple.com/forums/thread/109874 https://developer.apple.com/forums/thread/110829 https://developer.apple.com/forums/thread/109797

Of the threads you’ve listed, one deals with app entitlements to call the addPlan API, which is nice to have so a carrier app can directly provision an eSIM, but not needed for eSIM provisioning via QR code. For the other two threads, it’s the same person both times making the assertion Apple’s eSIM is proprietary, with all comments being 3 years olds and discussing a beta iOS version.

So would take all of those sources with a large pinch of salt. If Apples eSIMs we’re proprietary, I would expect to be easy to find articles discussing the fact, given they’ve been around for a few years now.