That was my interpretation at first too, but their anecdote about being heard from inside a car leads me to believe they're talking about cars seeing/hearing them on the road for safety reasons.
Is that the reason they rev up their engines to the breaking point while standing in traffic?
That's the biggest annoyance in my eyes.
As a motorcyclist, i think its ok for the engine to make some noise (not counting the obnoxious cruisers or bike with some aftermarket exhausts), but there is truly no reason to rev up hard while sitting in traffic or in a slow central streets.