Roughly speaking, yes.
First relative waypoints are defined wrt. the location/altitude specified in your flight plan. (For rotorcrafts this is also the origin of your local NED coordinate frame).
But if you use the common GeoInit block in your flight plan (which calls NavResetGroundReferenceHere) your current location will be your new reference.
Your waypoints will now be relative to this location (and ground_alt).
So if you have a <waypoint name="foo" x="-30.0" y="50" height="50."/> it will be relative to your location and ground_alt you set in the flight plan.
If you now start at a different spot than your flight plan location (and use GeoInit) all your waypoints will be moved relative to your new location including your new ground_alt.
Meaning the foo waypoint will be 30m west, 50m north and 50m above the position where GeoInit was triggered.