@roklenarcic If you have a spec :foo/bar and you conform any map that contains :foo/bar, it will get checked

spec.demo=> (s/def :foo/bar int?)
:foo/bar
spec.demo=> (s/conform (s/keys) {:foo/bar "x"})
:clojure.spec.alpha/invalid
spec.demo=> (s/conform (s/keys) {:foo/bar 42})
#:foo{:bar 42}
spec.demo=>   

So the s/merge with the unnamespaced key doesn't get conformed because s/merge only conforms the last spec -- ::b -- but the qualified keys all get conformed because regardless of whether they're even in the spec.

wait, so namespaced keys in maps get checks even if they are not in the spec I'm using to check them with?

Yes

You can confirm this with (s/keys)