My question was challenging the assertion of "the very core of the Alien concept, as it was once created by Giger".
Yeah that's fair too - again, I get what you're saying - and I agreed with it.
I don't think the original poster was going full dissertation either - looked like an offhand sort of summary that, yes, can be overbroad when looking for a wide perspective.
But I think the original poster was working from a narrower perspective around the point they were making at the time.
This is the sort of stuff I love about these stories - the people who built them took a simple thing, and rather than glossing over it - layered it full of other stuff if you look.
As far as the xeno life cycle - its one of the most scientific wild guess filled areas of the franchise.
How it works, especially for RPG purposes - is really down to head canon - how do you want it to work.
In Scanlon's _Book of Alien_ there's some comments around the cut food locker scene which were rationalizing how fast the thing grew by saying it had trashed most of the food supply - which also put the crew in a tighter situation of not just being limited by air (which Ash mentions in the workprint's cut scene meeting in the wardroom on how to find the beast after it escaped.)
There's also some notes about the alien being covered in slime at the end because it was cocooning up to wait it out until more food became available.
Ridley Scott has said in some places that the alien is essentially indestructible - re-affirming that at in the Covenant commentary.
To further add confusion - some sources said short life, others said long, some said both at different times (IF I remember correctly, Ridley has also said it was like a butterfly or wasp with a short life in earlier interviews or commentaries - a LOT has been said since 1979)
Now let's really muddy the waters: was Ash lying to Ripley about how the facehugger worked? Was its outer layer truly protein polysaccharides beng replaced with polarized silicon? How would that work with acid for blood?
The alien "acid for blood" was pure speculation in the first movie - "it must be using it for blood" ~ Non-scientist Brett "it's got a wonderful defense mechanism you don't dare kill it" ~ Non-scientist Parker.
The Leading Edge Games ALIENS Adventure Game and Colonial Marines Technical Manual by Lee Brimmicombe-Wood both try to sort out the biology and ultimately both got smacked by fans later - even if both were doing as much as they could with what little was available in 1991/ 1995 respectively.
This is one of the places where, personally, I think less is more.
Taking a page from Ridley Scott's playbook - don't explain this part - keep the players and their characters in the dark for as much as possible, as long as possible.
No one in universe knows how it works and everything is speculation and conjecture.
Leave yourself GM wiggle room by saying it works in whatever way it needs to at the time...
... this is a creature that, according to some, takes on characteristics of its hosts.
In effect, it's really THE THING meets H.R. Giger - and it can have all sorts of extreme abilities we (the audience) haven't seen yet in movies.
I think recently this has been retconned into black goo effects - but that too is up to you - the GM - and the kind of stories you want to tell in the setting.
We live, as we dream -- alone. ~ Joseph Conrad