Normally I'd agree; people overuse the term "Stockholm syndrome", but in this case it's a perfect analogy. Apple has you trapped. You can't use a competing smart watch even if you wanted to, because Apple is blocking critical functionality and there's nothing you can do about it short of ending the abusive relationship entirely and completely leaving the Apple ecosystem. But you don't want to do that, you love Apple too much, so instead you choose to thank your captor for holding you captive. It's your fault they have to do this after all; you can't be trusted to make a decision about which smartwatch you want to use. After all, if you chose a competitor that might be a bad decision that would hurt your security. So Apple is totally justified in preventing you from leaving. Thank you Apple for saving us from ourselves!

It would be one thing to acknowledge Apple's doing something bad here but still decide to use their products because you like their hardware. That would be a cost/benefit trade-off. But actually thanking them for the abuse itself? There's really, legitimately no better way that I can think of to characterize the situation than as Stockholm syndrome.