It has always been common for cars to estimate your speed a bit on the high side, because there's always a margin of error, and that way you don't accidentally go over the speed limit while thinking you're still below it.
But for a car to start beeping (or worse, interfering), they'd better use that margin of error in the other direction.
I can't stand all the beeping. It is wild how police are so against using mobile phones while driving (and they are right) but allow all these other distractions to run rampant in modern cars and distract drivers.
How we allow massive touch screens in Tesla's and other modern cars is beyond me.
But for a car to start beeping (or worse, interfering), they'd better use that margin of error in the other direction.