I feel it would be worth updating the help file:

Once a joint has been hyperextended, further ground controls will
not be possible to this person until they have healed. If the ground
control executed is a strike, however, further ground controls are
possible upon additional successful throws.

The help file does hint that once a hyperextension has landed (regardless of location) that no more of these strikes are possible.
So perhaps replace the above with:

Two types of joint hyperextension are possible, shoulder or elbow, once
a specific joint has been hyper extended, further ground controls will
not be possible to this joint until it has healed. If the ground
control executed is a strike, however, further ground controls are
possible upon additional successful throws.