Yes, I clearly stated “Watch-capable apps,” so your first point is moot, and in answer to your question, if the products are being made by the same brand and facilitating the interchangeable use of the same services, the answer is yes, logically, there should be continuity between the operation of the products.
Would you rather purchase an Apple Watch that requires you to search through the App Store’s Watch-capable apps, hunting and pecking for the apps you have on your iPhone, or purchase an Apple Watch, open the Watch app on your iPhone, and see a list of the apps you already use on you iPhone that have Watch-capability?
Would you rather have to individually set your iPhone, Watch, iPad, etc. to Do Not Disturb, or turn on Do Not Disturb on one device and have the rest follow suit? I know which I prefer. By your logic, when a company that makes cooking pots decides to start selling lids, they shouldn’t bother with making lids that fit their pots, because consumers shouldn’t expect the two different products to work together.
Your arguments against cross-device continuity have no legs to stand on.