I can't find any rule that says that's the case, or even any statement on the subject of nationality being a qualification - or not. No doubt it would lead to some submissions being ignored, but most likely that would depend on the context.I can't submit as I don't have English citizenship,
In particular, if you want to suggest that you (and others outside the jurisdiction) have a right of ownership based on being a descendant, I think that would have to be accepted. You could make the point that for some wills all the descendants are abroad. And estate administration, including probate, is an area which has always had to deal with parties all over the world.