I never noticed, doesn't help that you barely see Krang's Android Body's Face. From that clip this is a screenshot that I took to compare easier:
The realistic human one doesn't make much sense and not even the 1987 cartoon had a realistic face but I like it and it's the one that was used for the toy, so it was last minute decision.
But if we take a look at the design, it always went for a "realistic" look, no "silly" colors. Which was a mistake, the android body looks incredibly boring and generic; it was already a goofy film adding some red on the design wasn't going to break the "realism" of the film involving Dimension X.
So that's my theory they decided to double down on the realistic look for Krang's body to make it more "believable" and decided to remove the other human parts of the face so it would be more robot like. And I'm guessing they only kept the nose so it would at least somewhat resemble the original pink android suit.