I previously posted about Trello app false positive. Same story again with Tweeten app. This is also from Microsoft Store and BB was triggered after couple of minutes running. Also same reason "Behavior.TrojanDownloader" which I suspect that it's due some background sync? I clicked for allowing app, which if I'm right Anti-Malware Network will count with it for building reputation of that file.
However I'm just curious about reason why it's happening for Store apps. I checked file on VirusTotal and I found it's not signed. Could it be one of the factors?