As OJAS mentioned in a subsequent post, two different country lists are used. If I remember correctly, one list is uses for country of residence, the other for country of departure airport. Also for nationality, a drop-down list opens.
I didn't go back and check for Scotland or GBR, but I remember that for Switzerland, one list had the country code, ie CHE, the other list did not have it.
Anyway, that website is still very much "work in process", it seems, and the final version may be different. I'll look at it again when it will officially be in operation.