Everyone is making lots of assumptions...
Fact: We don't know that we were in a Citadel on Xen.
Fact: We don't know for sure if all Citadels on all Combine Controlled worlds are the same.
The Citadels we saw through the portal seemed to be hovering, where-as the ones on Earth seem to burrow into the ground.
Remember that if they were on Xen, they might not be able to burrow because not all Xen landmasses are dense. Also, there might not be much in the way of metal on Xen, and so it might just be more efficient to use native materials.
Perhaps the first Citadels were like the ones on Earth, and then later, their structure was gradually replaced with natural Xen organic and rocky materials. If the Combine did control Xen, we have no idea for how long. It might have been five months, it might have been five-hundred years.
The Citadels on Earth initially appeared in the ground manufactured from alien materials, however some have suggested that the strange walls seen 'eating' the city may be taking the rubbel and processing it at the Citadel. S it is possible that in time, perhaps a very long time, that the Citadel(s) will eventually resemble Earth structures or materials more-so than they do now. However, this is only speculation. All of it.
Any of this information can be interrprted in different ways.
There is one thing though:
Vortigaunt and Nihilant Quotes. I don't know any perfectly off the top of my head. However I seem recall hearing that Nihilant says: "Slaves. We are their slaves."
And Vortigaunts: "We must achive total victory, or suffer our own extinction. There can be no more compromise."
The Vortigaunt quote could be interpretted in different ways, however Nihilanth's quote is pretty convincing to me.
I will admit though that I'm not positive of the Nihilanth quote because I didn't hear it myself... I've always found it hard to understand what he's saying. I'm sure there is a way to verify it though.
Fact: We don't know that we were in a Citadel on Xen.
Fact: We don't know for sure if all Citadels on all Combine Controlled worlds are the same.
The Citadels we saw through the portal seemed to be hovering, where-as the ones on Earth seem to burrow into the ground.
Remember that if they were on Xen, they might not be able to burrow because not all Xen landmasses are dense. Also, there might not be much in the way of metal on Xen, and so it might just be more efficient to use native materials.
Perhaps the first Citadels were like the ones on Earth, and then later, their structure was gradually replaced with natural Xen organic and rocky materials. If the Combine did control Xen, we have no idea for how long. It might have been five months, it might have been five-hundred years.
The Citadels on Earth initially appeared in the ground manufactured from alien materials, however some have suggested that the strange walls seen 'eating' the city may be taking the rubbel and processing it at the Citadel. S it is possible that in time, perhaps a very long time, that the Citadel(s) will eventually resemble Earth structures or materials more-so than they do now. However, this is only speculation. All of it.
Any of this information can be interrprted in different ways.
There is one thing though:
Vortigaunt and Nihilant Quotes. I don't know any perfectly off the top of my head. However I seem recall hearing that Nihilant says: "Slaves. We are their slaves."
And Vortigaunts: "We must achive total victory, or suffer our own extinction. There can be no more compromise."
The Vortigaunt quote could be interpretted in different ways, however Nihilanth's quote is pretty convincing to me.
I will admit though that I'm not positive of the Nihilanth quote because I didn't hear it myself... I've always found it hard to understand what he's saying. I'm sure there is a way to verify it though.