If the latter is the case, well, then you need to allow it somehow... There are several ways of achieving this depending on your environment and business requirements. For example, you could have the same AD group assigned to the "wetransfer" rule and a rule that would allow "ssl and web-browsing" to the "Online Storage and Backup" category (that category would need to be set as the matching criterion, on the "Service/URL category" tab; the URL profile in that rule would need to be set to "Alert" only on all categories).