This issue is really annoying. Is there anything one could help to fix it?
I noticed that there is now a second issue created in Jira: JS-505 next to JS-90, which could be marked as dup by someone with write access to Jira 
In cases where a function should handle all cases of e.g. a enum within a switch, we actually prefer to have no default return, to ensure in case the enum might be modified (which might come form an external API) we get a a compile error. So at the moment, I quite often mark those cases as false positives.