It's really just about the sound. Jon Porter's Verge review is one of the ones I read. He calls them "competent", but:

Fairbuds XL don't offer a particularly detailed sound… Listen to a layered track like Paranoid Void's "Null," and the Fairbuds XL make it harder to hear the separation between guitar and bass. It's the same with Max Richter's "On the Nature of Daylight," where all the string instruments feel less distinct.

LTT (video) didn't like the emphasis on bass, especially at the expense of the mids, and the measurements at 11:05 seem to back that up.

My own taste is somewhat the opposite of this profile. Sometimes I want bass, but I often find it overwhelming and every Bluetooth headphone I've tried is a little too warm for me out of the box. I'm losing some hearing in the upper mids, so having them drawn back like this isn't good for me.