I would like to add the use of "taps" as an engagement metric to your list of misuses of telemetry. There used to be a rule of thumb in UI design that important actions should be as few clicks away as possible. Measuring engagement through taps encourages the opposite.

I also don't like things measuring "dwell time" when scrolling, as it encourages attention-grabbing gimmicks and rewards things that are confusing as well as things that are useful.