The point was for an established universal term to be used. Everyone keeps saying void elves and blood elves are high elves and in the next comment they will say they are all thalassian elves.
The fact is reality has changed. High elves are no longer the sole type of thalassian elves. Therefore it is no longer practical to call the physical race high elves/quel’dorei. The physical race is now thalassian.