The backup alarm is a global setting applied to all alarms. Please allow it to be configured per alarm.
Some alarms are not meant to wake me (e.g., silent reminders), so the global setting forces a trade-off: either disable backup alarms entirely or avoid using the app for certain alarms (which is very useful for me as a reminder app).
Adding a per-alarm backup alarm toggle setting (and ideally adding all backup alarm settings to per-alarm settings) would make the feature much more flexible and usable.