I roughly agree with you but in your deps.edn example, how would you like the tool to respond? Your map/dictionary/object has an uneven number of forms, so what else would you like it to say?
I think their should be a "lein-for-deps-template" that subtly guides people in the right direction by starting the project up with 2+ dependencies. Lein dodges this by using a list-of-list data structure where this mistake is harder to make (copy and pasting stuff in brackets is the right strategy in lein) and there is much more boilerplate in a project.clj to hint what our aspiring Clojure programmer needs to fill in.
My problem here is that the entire way through that story, at no point is there a simple prompt in the official reference documentation telling people what a deps file with multiple dependencies should look like. Even finding the examples of 1 dependency is quite deep in and seems to be an advanced topic (you'll note the sibling comment that considers dependencies an advanced topic for people who already know the language well enough to reflexively get maps right, and it says a lot about the actual complexity of deps that the official guide to installing dependencies thinks 2x dependencies is out of its scope).