"We added a new Beryllium tweeter, which was co-developed with Seas. It extends the frequency range and has 9 dB less distortion than our original tweeter." (
https://www.grimmaudio.com/hifi-products/loudspeakers/ls1be/)
It does not tell what kind of distortion, but I guess their statements are in some way true. Sadly I didn't listen to original and be in comparison. But I could assume, that lower distortion is always nice to have, when you want to turn up the volume. Sound-wise I do not have a lot experience relating to different cone materials.
Would really like to get a pair (or even three pieces for FL,C,FR) of these be-Tweeters. Just saw them in an inwall Speaker from Meridian Audio, too. But not 100% sure, if they share the exact same parameters.