iPhone 15 Vibrates When Outgoing Calls are Answered

As far as I know, the only way to turn it off currently is by going to Settings > Accessibility > Touch > Vibration. Note this will also turn off vibrations for emergency alerts, so personally I would keep that on as thats more important than call vibrations.

You can submit feedback to Apple below for a separate setting to turn this off:

Feedback - iPhone - Apple

Hard to know whether people that don't submit feedback are for it or against it, and after all Apple has a few billion users around the world, so you can't assume they all don't want these features. You would need to submit feedback against it, and I've already seen quite a few.

I haven't tested it, but I wonder if doesn't have something to do with the new setting for automatic hold detection.

Might try turning that off in Settings>Apps>Phone and see if it makes a difference.

I can't find that setting Tim.