Nonsense.

The "rule of thumb" is that you are at risk of hearing damage in an environment where you cannot talk comfortably at normal voice level with somebody at arms length away.

I have owned many laptops in my time (including Macbooks). I have frequently pushed them hard (e.g. compiling code) to the point where the fans run for extended periods of time.

Not once have I had difficulty conversing in a relaxed normal fashion with somebody with arms length or even further away in the room. I've never had to raise my voice.

Its simple, if you don't believe me, get a calibrated decibel meter and take a reading in a controlled manner in a controlled environment. Frankly I'm willing to bet you hard money that the measured sound level with the laptop fans running at full whack will not be anywhere near hearing damage level.