The design requirements cover both cases, vertical and horizontal overlod.
Gear load specs are worthless after failure when the engine/wing contact ground at the variable of airspeed/ dynamic force. The gear "shear safety" info being discussed becomes a non factor after the fact.
To state that even if gear load factors had not been exceeded but a sufficient strike had occured on the wing or engine the outcome would have been the same. DFDR released data will clarify all of this.
Why all this speculation. Obviously the aircraft experienced a contact with the ground out of operational limits resulting in a bad landing, obsolute the only type of bad landing....
Respect the operating limitations of the equiptment you are operating, understand this through and through and the odds of safe operation are on your side.