1. When providing your "criteria" of a simultaneous catch, you did not restrict the scope to airborne opponents, thus leaving the impression that those conditions always have to be met for a simultaneous catch. That's misleading; I agree that what you say applies specifically to the case when both opponents are airborne, as in 7.5.4.
2. Consider the reverse play: A is airborne, possesses/grasps the pass, and while he's still in the air B, who is on the ground, grasps the ball as well. As A comes to the ground, they both go down holding the ball.
Are you really going to say, (a) this is not a simultaneous catch, despite the definition in 2-4-3 (which part of "joint possession" does this play not exhibit?), (b) that B caught the ball, because he was on the ground and A was not, and (c) that B should therefore be credited with an interception? That ruling seems patently wrong to me.
If you deny (c) and give the ball to A, then you're defending a distinction without a difference.