I worked in a Nabisco factory a decade ago in the US making Oreo.

They've consistently looked for cost cutting measures to reduce the amount of cocoa powder (expensive input) put into the product. What happened when I was there was they would look for a new vendor that would offer stronger cocoa flavor profile per kg and then use that as a justification to cut the amount of cocoa powder in the product. To mask it they would amp up the sweetness.

In a blind test, a normal people can't tell the difference year to year, but if you compare it to what it was ten years ago, there would be a noticeable difference.