But that's another advantage of the 2hbh: Even if it is taught poorly, it is often still good enough for a player to get by with. Whereas a 1hbh taught poorly is just a disaster and possible health hazard.
One other point, the standard grip for the 1hbh in the U.S. is the Eastern grip. Nowadays this grip is just too limited in range (esp. for high balls), which necessitates a lot of forward/back footwork discipline and probably requires the student learn to hit a decent slice as well.
So unless the default grip changes to Strong/Extreme Eastern or "SW", the 2hbh will have too many relative advantages in learning and performance.