It was offered in the negotiations prior to the invasion.
You are right that it couldn't have been the capital.
At the time, I incorrectly believed townslands *could* be declared capitals hence later on in the invasion's early days, Seoras being very serious about removing Barca from Shinnen Purlieus so it couldn't be declared their capital, and then D'hara from Shinnen Purlieus, so that it couldn't be given to Barca to be made their capital.
I don't believe the fact that Barca couldn't have a capital in townslands was mentioned in negotiations (of course, this was all back in May/June of last year...), just that they wanted Shinnen and that D'hara and Fissoa refused to provide a single region for Barca.
