The existing "simple  case" case was the equivalent of registering with a single tag.  We didn't want to support both register_with_name and register_with_tag, because then things get complicated and you'd need to support use_with_name vs use_with_tag.

It's easier to just flip the order of the parameters, so name/tag can be splatted.

Is there a use for name that I'm missing?

The simple use case is the equivalent of registering with a single tag, not without a tag.  Things will get complicated if we mix registering with tags and names (because then the Pacto#use