I just stumbled over this when trying to figure out why process.env.FOO (without js/) produces no warnings and noticed that pretty much all symbols with dots will resolve and sort of work accidentally. They also never produce any warnings.
When trying to fix this I stumbled over a lot of code that sort of relies on this behavior. Most prominently defrecord and exists?.
defrecord can easily be fixed since it uses cljs.core.MapEntry  instead of cljs.core/MapEntry. cljs.core.MapEntry resolves to cljs/core.MapEntry and pretty much all dotted symbols will resolve to the first segment turning into the namespace. This works since munge turns / into . later on.
exists? will split some.nested.Thing into checking some, some.nested, some.nested.Thing which again is some, some/nested, some/nested.Thing. I tried fixing this directly in cljs.analyzer/analyze-symbol by properly desugaring some.nested.Thing into (. (. some -nested) -Thing) but this is insufficient since macros can directly call cljs.analyzer/resolve-var with dotted symbols (eg. exists?).
At this point I'm unsure how to fix this. I do think this is worth fixing but it may produce lots of warnings in user code. Is that acceptable?