Currently that is the way. When an account shares a device installed on that account to another user, the shared user shares the detection and notification settings was the the original account. Currently there is no way to customize shared user permissions when sharing any type of device. Currently shared users are restricted on cameras from viewing the SD card playback from the shared camera and accessing some settings.
There is a current wish list that is tagged in progress and researching that could use your support by commenting and most importantly voting on to help further it.