That FAQ is no longer correct after version 1.5 of the rules. So Superhuman Strength is NOT discarded in the attacked enemy is stunned. There is a new FAQ regarding this exact situation:

13 – Hi, about SHE-HULK “Superhuman Strength”
Forced Response: After She-Hulk attacks, discard Superhuman Strength → stun the attacked enemy.
ruling 1.5: Cost […] – An ability’s cost cannot be paid if that ability’s effect requires one or more targets and there is not at least one valid target.
If SHE-HULK with “Superhuman Strength” attacks and defeat an enemy the sentence “stun the attacked enemy” seems to have no valid target so, did the “Superhuman Strength” is discarded?
same question if SHE-HULK attacks a already stunned enemy?

To answer your question(s):

No, Superhuman Strength would not be discarded in either instance.

The main reason being, under the updated entry for “Forced” in the rules reference, we have made a ruling stating that if a forced ability requires a valid target but there is no valid target, the ability does not initiate. If an attacked enemy left play before the Forced Response on Superhuman Strength triggered, there is no valid target for the ability, so nothing happens. It’s similar if the enemy is still in play but cannot be stunned (e.g. because it’s already stunned); the Forced Response does not initiate.

-Alex – May 25, 2023