"The Chestburster was probably the biggest and most confusing curve ball
of the entire film. Instead of the snake-like, infantile Xenomorph
offspring seen born from every Human host in every Alien film before it,
the Chestburster born of Oram was born complete with a full elongated
cranium, arms, legs, second jaw and tail. It literally looked like a
miniature adult Xenomorph. There were no aesthetic cues to insinuate
this was an infant by any means besides its miniature size.
The concept of cocooning, shedding those cocoons and developing a
hardened exoskeleton were completely thrown out the window and within
minutes this Chestburster, or what should be called “Minimorph”,
developed into an overly organic looking, adult Xenomorph.
I would have
loved to see a similar scene where one of the surviving crew discovered a
shed cocoon and were then introduced to the adult Xenomorph, similar to
the original Alien. I’m not sure why they chose to introduce
the Chestburster this way and I see them having a hard time explaining
how we go from Minimorph to iconic Chestburster before we really come in
the back door of Alien.....
....Of course, a big question everyone had since day one of Covenant’s
production was what became of Dr. Shaw (Noomi Rapace). Sadly, like many
of us speculated, Shaw is deceased by the time the Covenant crew
arrive. David’s attitude towards Shaw and her fate was a puzzling one –
he seemed to have adoration for her, but as we later discover, he had
not buried her in his garden, or kept good care of her remains – but
instead had used her for his own twisted experimentation.... This solidified David as a truly
evil and twisted character. "
- Chris' review of Alien: Covenant
It does seem Ridley Scott has disowned certain key features of his own movie Alien (1979) that was key to establishing the franchise of how the Xenomorph grows. No idea why he broke away from established canon, unless he intends to change back to the original snake larvae and moulting-cocoon system when it is explained how the Xenomorph becomes like the ants on Earth, with queens, soldiers and workers.
Looking through the movie save for a detailed sketch of Dr Shaw's mutilated body in a set of scrolls and the android David saying he would do to Daniels what he did to Shaw, it was hard to find any other detail of the fate of Dr Shaw.
It is likely she wasn't attacked by a facehugger, but from the mutilation she was probably a victim of David's first experiments with parasitic wasps laying eggs that hatched into larvae that ate her inside out, and not a victim of a facehugger as Wikipedia's current edit of the article on the movie says.
Either way this story showing that David's twisted experiments had something to do with creating the Xenomorphs destroy the mystery and our deepest fears of going into vast unknown of space that was probably what the first Alien aimed for. Sort of like the Predator representing our deepest fears associated with the unexplored tropical jungle.
Ridley Scott's interview here confirms that the Xenomorphs are the creation by David at 3:20, and disses the Alien vs Predator movie series at 5:05:
"...If that is what happened to Shaw it is beyond stupid.
Prometheus was opening the door for a massive universe full of
posibilities in story-telling. Covenant seems to be trashing all of that
and having David as the creator in full [dis]regard.
If he's the creator
then how the hell does a 2,000 year old ship with a chestbursted
fossilized alien come into play that precedes anything David may have
done? Yeah unless Scott pulls [a] Hail Mary and brings the engineers and
their story in full force I'd say it's safe to say the franchise is
cooked. Ironically even Ridley said it himself when he said the beast
was done. Just more of the same brainless crap."
The general conclusion at the end of Convenant is that never trust a megacorporation like Weyland Yutani, or its assets like its synths. Instead of being the lifeline for colonists light-years from home, they become the death of everyone on board out in deep space with no rescue in time. It seems the moral of the story is to avoid getting on board a deep space colonization project funded by a private corporation. Probably a better idea when exploring space would be to have one's own spaceship and to be ready for everything and anything.
Overall this movie sticks with the the dark storytelling and dark endings for characters in the Alien franchise including the protagonist survivors like Dr Shaw, Daniels and later Ripley before she was cloned. It does make me wish they could continue the Alien vs Predator franchise just so I can see the heads of a few corporate scumbags and evil, twisted androids from Weyland end up in a Predator's trophy room.
I did like the Xenomorph's own POV in the main ship, almost mirroring that of an extremely angry person with affected vision from his incensed rage with those little twisted fiber like lines on its otherwise clear vision.
I will probably add more thoughts if they come up.