Why do half the features on the apple watch not work when set up with Family Setup?

Some features require the iPhone because of patent litigation (Blood Oxygen), and requiring the iPhone to be in the mix side-steps the patent suit.

as mentioned by others, we cannot do anything about the way the Apple Watch works. But you can send feedback

Apple does not read this user-to-user technical support forum for feedback.

Feedback - Watch - Apple

re things like exercise in minutes rather than calories, and heart monitoring, Apple presumably don't want our adult hang-ups foisted on our kids.

Buy him an iphone and set up a new Apple account with a date of birth ten years earlier and he can have full access to all, if that's what you want.

Re battery, Using an Watch without an iphone in your pocket will also use the cellular plan a lot more which is a battery burner.

Because those features require that the device be used in conjunction with an iPhone.

No. there is no way to bypass the restriction.

The Apple Watch does NOT measure blood pressure at all. It monitors for signs of possible hypertension.

The calculations necessary to do that take place on the phone, not the watch.

The watch does not have sufficient processing or storage to perform some tasks. those are done by the phone the device is paired to.

poodleschool wrote:

Blood pressure monitoring requires an iphone to function? How does that make any sense. The blood pressure is measured via the apple watch.

That is the way Apple set it up. You can let Apple know you'd like to see something different here:

Product Feedback - Apple

poodleschool wrote:

Apple Watch 9 does

No it does not. You are mistaken. No Apple Watch measures blood pressure, period. Blood oxygen levels are measured, not blood pressure. Do you understand the difference?

Why? Because the way you assume it should work and the way Apple built it to work are two different things.

poodleschool wrote:

Apple Watch 9 does

False

It does NOT measure blood pressure. It can monitor for signs of hypertension.

Hypertension notifications on your Apple Watch - Apple Support