The SD card is not for the alert notifications, it is for the “Record on event” or “Continuous recording” that is controlled in the app for each camera under “Advanced Settings”. The 12 second alert notifications are configured in “Event Recording” under “Detects motion” and “Detects sound”. If either of those is toggled on, then alert notifications are sent to the Wyze cloud storage, with a 5 minute cooldown between events. In order to view those events, you select them on the Events page and they are then downloaded to your phone.
Please let me know if that clears it up for you.