I almost typed that they were probably joking, and Tesla wouldn't allocate the kind of development hours needed to make very quiet motors make a tiny bit more noise (A/C motors can be made noisier or quieter through resonance tuning).
But...then I thought about that Tesla is already under a permanent magnifying glass. The "world" wants to prove that electric cars are unsafe, and perhaps there's a possible threat of some jurisdictions trying to punish EV producers by making a pedestrian audio alert requirement retroactive. So perhaps Tesla wants a way to have the cars without pedestrian alert speakers generate some noise just in case someone threatens an expensive mandatory recall at some point.
When you have a lot of enemies, it pays to be cautious.
That's precisely why I believe it's a contingency at best. I don't think it would be a chatter though, there are things you can do with alternating to make a induction motor "howl" more at low speeds. The question is whether the labor time is worth it to find the perfect configuration, and make sure it doesn't cause damage, or lessen the life of the motor or battery, or become obnoxious to the driver.
An electric motor operating at max efficiency will make no noise. So forcing the motors to make noise is essentially making them operate at an extremely inefficient manner. This would go against the very essence of Tesla. Not to mention the added wear on the bearings and coils that it would induce. I would put this together with the rest of the rumors that have no basis in reality and anyone with a small amount of engineering background would understand to be nonesense.
It seems that bicycles, scooters, wagons, skates, and perhaps walkers might also require noise generation.
I am repressing my urge towards even more obsurd sarcasm.
I chose not to mention wheelchairs or noise pollution.