[AlexanderHowl]

I do not think that Extra Attack is an upgraded form of DWA. If it was, you could not use Extra Attack with Rapid Strike, as you cannot use DWA with Rapid Strike. Since you can use Extra Attack with Rapid Strike, you can use DWA with Extra Attack. For example, a martial artist with Extra Attack 1 could use one attack maneuver to kick once with Kicking and then trade their second attack maneuver to punch twice with DWA (Karate).