So you mean the head? That looks apart of the suit to me, it looks sewn onto the body suit and the way the mask is sewn on is identical to how it was on the white suit.
I don't see why they would leave the head exposed.

BlueBasilisk#830480 wrote:Our best view of an unarmored Eva yet! Mark.06 has a lean, tightly muscled body, a lumpy, egg-shaped head with little ears, and dark greenish grey flesh:

How can you tell it has dark greenish grey flesh?
To me it looks like it is completely covered in its dark greenish grey suit.

Okay, what if there's another time skip and suddenly see them as adults though? I guess that would work but I don't see another time skip happening at all. We haven't even figured everything out about the last timeskip, another would make things even more confusing. On the other hand, I also see th...

Even if it could be broken I doubt they would instantly age physically to appear how they should be for their ages, rather I think they would just lose their eternal youth and begin to age at a normal rate.

Watching these rebuilds it seems like no matter what happens Gendo will say it was a part of his plans