Why did they remove the clouds?

If you noticed on the Blu-Ray Diamond Edition version, the retreating clouds forming Mufasa's ghost are gone when Simba is running towards it. They were there in the original 1994 version released in theaters, Laserdisc, VHS, and the 2003 Platinum Edition VHS/DVD. Along with George Lucas, Disney is notorious for making changes to their classic films when it is re-issued to the public. While this change isn't that major of a deal as Greedo shooting at Han first in Star Wars Episode IV: A New Hope, why was this change (or should I say deletion) even necessary?