I think that you may be missing that most English speaking people have a middle name that they rarely use for anything except filling out documentation. It's relatively rare to not have a middle name in English names, though you can obviously see how many actually use them. Even in official contexts it's often omitted. My US issued credit cards just don't even have them and even my driving license from Illinois (de facto ID) only uses the single letter initial.

In your example that is a single name but there will usually be an additional middle name. Marie-Claire Elizabeth Jones or something like that.