It's true...slight change of a hairline, wider eyes...lots can change things to an unrecognizable degree in some cases. If you look at blank sculpts from some artists, and then see the final paint job, it sometimes actually ruins a 100% spot on sculpt of a character...it's pretty crazy!
Yeah, I call bullocks on the reasoning in the first picture still...there was no chip, it's too perfect, and the eyes and even the skin tone are different. All those things change things. It still looks pretty good, and I'm sure it'll look fine in person, but it's silly to come out and say, "We meant to make the prototype worse, like the final production piece, but accidentally broke it for the better while taking pictures."
As for the third head, anyone who has been reading All New X-Men should love that take on young Jean! It's definitely a completely different option -- that was kind of done by accident as well.