Your expectation matches the original iteration of SE‐0226 as written. (When it was implemented in Swift 5.2, the target dependency erroneously used the last path component instead, which was fixed in some later version.)
Around the time of SE‐0292, SE‐0226 was amended to eliminate the name attribute, and now you are supposed to specify the identity, which for a URL dependency is the last path component. I do not remember at what version that change was actually made, but it think the implementation does properly distinguish each side of the tools version.
Speaking for myself, I am on the fence about which is better. On the one hand, I prefer the full freedom of the text string over the restrictions of the identifier, but on the other hand, the simplification does result in less parameters. So I ended up not really participating in that review. But with hindsight I can say that the whiplash has been as confusing as it was annoying. And so I cannot imagine myself supporting a proposal to flip it yet again.