In Garmin Connect, underneath my device (Edge 830 in my case) on the right side, it has a setting called "Elevation Corrections" and the pop-up states:
Elevation Corrections are calculated with data from professional surveys instead of the data from your device. If your device has a barometric altimeter, Elevation Corrections are disabled by default.
My Edge 830 does have a barometric altimeter, so the corrections are disabled. But wouldn't the elevation data from professional surveys always be more accurate than the barometric altimeter data (which is affected by variations in barometric pressure)? Why would I want to leave the elevation corrections disabled, just because my device has a barometric altimeter?