The one column layout isn't really a thing. 😀
Well that's not quite true. It's a thing. But everything is "one column" unless something else is specified. So no special classes are required.
What would we name the class anyway? The option 'col-1' isn't consistent with the other columns classes, but 'cols-1' confuses certain kinds of minds because it combines a plural and a singular concept in a single label. 🤯