In the last 10.2 PTR build, Undulating Sporecloak's shield has been halved, compensating for the nerf with a Versatility buff while above 70% health.
Undulating Sporecloak was a very popular item in Patch 10.2, especially when pushing for high Mythic+ pushing. This is due to it's unique effect of a massive shield when you hit low health, likely saving you.
Considering Embellishments don't seem to be too much DPS in the grand scheme of things, many players opted to wear this for survivability and it's possible that more guilds may have ran this on prog had they know about it.
However, in Patch 10.2, the shield value has been cut in half, but players will gain a Versatility buff while above 70% health.
This will reduce the saving potential of the Sporecloak, but it does provide some offensive benefit now.