Doctor M said:

I maintain these changes are deliberate not accidental. Left in their original state, I think it would cause problems when viewing in 3D.

What disturbed me most is that Ariel is repainted to look like her grotto is in full daylight.

I am Flounder's sigh.

Disney has outright admitted that it's an editing error that occurred when splicing the film back together during the restoration and conversion process. Probably the same reason why the Scuttle fade is missing too. It's not deliberate, it's lazy.

Also, it's not so much "repainted" as color corrected and contrast punched. The DVd in the clip has a heavy red hue missing from the Blu, and the Blu is A LOT brighter. I'm hearing this release has a remarkable amount of untouched grain. Even the original Grimsby error fixed on the Platinum is back. It's source from a whole different print.