I take your question to be rhetorical. It's a version of the reciprocity. I explained that if somebody is a Canada-U.K. citizen, the country that ends up with them is simply the last one to get to the revocation of citizenship. There's obviously an arbitrariness to that.
Your question draws on the ideas of to whom do we belong and what does belonging mean? We often talk about “belonging” in a very rich sense when we talk about what we expect people to experience as Canadian citizens, but when it comes to removing them elsewhere, we rely on the purely formal possession of legal citizenship as a valid basis upon which to deport them, because they really belong “over there”. I think your question exposes that fault line in how we use and understand citizenship.