RUNNING POWER

If you mean via ActivityInfo.currentPower / maxPower / averagePower, I can only assume it's because historically, those fields were only for cycling power, and FR165 does not support cycling power.

I'm not saying it's a great reason, but it's an explanation that fits the facts.

Also, ActivityInfo.*Power did not always reflect native running power. This is only a fairly recent change, even for some devices like FR955 and Fenix 7 which had native running power from the start (although originally, they did not support native running power from the wrist.) It actually broke a bunch of CIQ fields which showed running power from Stryd in run mode, by asking the user to natively pair it as a cycling power meter. Since ActivityInfo.*Power is now native running power in run mode and cycling power in cycling mode, instead of cycling mode in both cases, that workaround doesn't work anymore.

Then again, VA6 doesn't support cycling power, but it does support running power and it's a supported device for ActivityInfo.*Power according to the API docs.

So maybe Garmin recently changed their mind on this apparent policy.

It's kind of like how navigation-related fields in ActivityInfo aren't available for FR255/FR265 (and other like some of the Vivoactive models), even though those devices support navigation. It's kinda baffling, but my only guess is that it's because those lines didn't historically support navigation.

Maybe none of it really makes that much sense.