Oh, I wouldn't want to try and coin a name for it if I were in that position as a researcher. No matter what you choose, someone will be mad.

It did grow in a similar manner to a fetus brain, but it is also missing parts, those being the 1% of genes that aren't present.

"Fetus-like brain" works and is less ambiguous.

Warbling.... Man. I really need a break from the pre-1900 novels for awhile. At least until I stop my unthinking use of archaic terms and phrases.