That is an advertised feature, so I assume that the lawyers have looked into those health claims as somewhat defensible.

First, they do seal, so even if it's not as tight as a foam earplug, it is something.

Second, there's the ANC which is producing out of phase sound and lowering the sound pressure level reaching your ear. I have seen commercial hearing protection with ANC, though I'm not sure if it's allowed to be advertised as such. The theory is sensible at least.

Thirdly, the ANC is allowing you to listen to your audio content at lower volumes, especially in a very loud environment like an airplane.

Fourthly, there's an advertised hearing protection feature in passthrough mode where external noises loud enough to cause hearing damage will be automatically reduced.

Fifthly, There are sound pressure measurements being sent to the iphone for audio content loudness in real time, and also over time notifications you receive if you have been listening too loudly.

So all in all, yes in practice, but we're not exactly talking OSHA here.