It's the people crying conspiracy when Velocitron Scourge was released.
"They made him the wrong colours on purpose to sell him again!"
No, they didn't paint the translucent pink bits on the robot mode silver because the silver paint budget was used up by the trailer. That's all.
Fans tend to build elaborate mind palace scenarios to justify certain things.
"They aren't a fan of this thing, here's my psychological evaluation of this fan site interview."
No man, it's not that deep. It's just budgetary.
No, I think the issue is the design team likely doesn't know what things will look like in packaging. If they think Scourge is being sold in the at the time typical leader class packaging, in Robot mode; with a window... Well... He's gonna look almost exactly like Legacy Optimus Prime.
Here is a custom I found next to Legacy Prime, Imagine these two showing up on the shelf at the same time, in open boxes like Kingdom got:
Two mostly grey and black trucks of the same exact mold. Making Nemesis Scourge, means that if we assume that at the time of design they have no idea that the leader class boxes were going to be changed to closed boxes, makes sense to make Scourge look more visable distinct and not like literally the same toy sold to you twice.