It was my understanding that the MailAPI.viewFolders() used further up was the async call to determine the accounts, and that these changes were for fast initial load, so a synchronous value we can check quickly was better for those purposes. 

I am open to doing a change though in this area, but would likely need input from @asutherland as for how best to do it in a way that would be fast and fit with the mailapi model.