Your statement is incorrect. Sentry mode records video from all 4 cameras and NOT just the dashcam.
No, it's not incorrect.
Sentry
does not record anything. Ever.
Dashcam does.
Dashcam is not "a camera"
it's the specific name of a Tesla software feature that records 4 cameras feeds at the same time.
Dashcam, if the car is awake, on, and there's a storage device properly attached, is
always all 4 cameras to the storage device. That's the
only thing that records video to the storage device.
Sentry, if on, keeps the car awake. And if it goes to alert mode will move the last 10 minutes of
dashcam recorded video into the sentry folder. It
does not record anything.
If you are unclear on this try the following:
Turn OFF the dashcam recording.
But turn Sentry mode ON. (verify dashcam is still off).
Now wait a few minutes. Then do something that would cause a sentry alert.
Check the storage after. There won't be any video. Because sentry does not record stuff, it only moves existing dashcam-recorded video to the sentry folder.