How would the custom app disable the native Watch services?

Good point, consumers should all simply develop their own apps instead of buying a product.

I just went through this yesterday. My wife and I both have Apple Watches with LTE and I was rolling them over: both phones and my watch ported easily but the second watch wouldn’t show up on the account at all with no explanation. The first support person couldn’t see a problem with the details they were able to see, the second level one could see a fraud hold for non-specific reasons and forwarded us to a fraud team who verified my identity and back to a third person who solved the problem by deleting and recreating the line on our account. Every one of the people I talked to was clearly trying to help but their billing system sounds like it’s someone’s old house primarily consisting of duct tape and stucco.

This is a disappointing contrast to their actual network which is clearly run by people who take running a reliable network seriously with good coverage and latency.

In what way are watches with SIMs (or eSIMs) not just tiny cell phones? Or is you meaning that the modern smartphone is itself a “pile of hacks sitting on top of hacks”?