They aren’t the only one claiming a Black Cauldron remake. Disney reacquired the rights to the entire Chronicles of Prydain 3 years ago and are supposedly making it into a Disney+ series. Treasure Planet’s remake has also been reported in many places.If you search their website (I posted a screen cap) you'll see them claiming live action remakes of Black Cauldron and Treasure Planet.
And it’s not hard to believe that Disney is developing more live action remakes on all their other films. Although I know nothing about the quality or accuracy of that website, criticizing them for this seems like overkill.