Is that confirmed? Seems a bit odd.It was a beholder, WotC just refuses to let CR use the product identity stuff. Which is why certain creatures don’t appear and some spells are renamed. It’s Cat’s Claw instead of Bigby’s Hand. Widogast’s Nein-Sided Tower instead of Mordenkainen’s Magnificent Mansion. A person with nine eye stalks that shoot beams that just happen to almost perfectly match a beholder’s eye beams, but not the angry floating no-butthole having rage monster. Etc.
There were absolutely no problems using the product identity stuff in campaign 1 (from Bigby's hand to the Magnificent Mansion to beholders). And now, they're even more intertwined with WoTC, from having an official supplement out to having one of the lead WoTC guys on the show once or twice.
And as @Parmandur said they use WoTC IP all the time - Matt made a point early on to use Volo's and Mordenkainen's new stuff.
I thought the name changes were more a flavor thing.