That’s interesting. I can see why you would not want the alarm while in bluetooth mode, as there is a good chance you’re away from home and there’s no known way to turn it off. On the otherhand, in case of a power outage, network outage, or simply forgot to take Roam off bluetooth mode while at home, you would still want the alarm to go off as normal. Indeed old style clock radios had a battery back for when the power went out.
Might be good idea for Sonos to have a setting for how the alarm should function while in bluetooth mode, so you can at least choose the behavior you want in advance.