I don't know what the Explorer cruise control problem actually WAS down to, but it makes perfect sense to me that it could have made no difference to this problem whether or not he'd had the recall done.
A cruise control system will have a variety of sensors and actuators (and probably some software too) in order for it to work. If the recall was (say) for a faulty brake pedal switch but this problem was caused by (say) a faulty throttle actuator, either fault could have caused a cruise control malfunction, but having had the recall for one component wouldn't necessarily prevent a different componet from causing it to malfunction.
With regard to the handbrake, I don't think it would have made any appreciable difference. The Explorer is a big SUV. I am assuming his might well have been an automatic too. (Otherwise putting the clutch down would have been a very easy way to solve the proplem)! If you pull the handbrake on, the vehicle will just open its throttle a bit more to get back up to the speed at which the cruise control was set to. If the engine didn't have enough "grunt" to overcome the handbrake drag, the gearbox would have automatically shifted to a lower gear until it did (as far as the car was concerned, it would have just encountered a hill). I can't think of many cars where the engine can't overcome the handbrake WITH EASE once it's driving along at such a speed. After a minute or so, the handbrake pads would have been faded to death anyway.
HOWEVER, that still leaves a number of other unanswered issues.
The first one (which everyone has mentioned) is why the hell didn't he turn the engine off. Your explanation of panic is the only one that makes sense to me. Next, why didn't he jab the throttle? On mnay crusie-control-equipped cars, touching ANY of the pedals disengages it. He's have been jolly unlucky for BOTH to fail simultaneously!
The next question is why he didn't take it out of gear?
Finally, although one wouldn't expect a handbrake to be able to slow a car down, the footbrake certainly should have done! Apparently, it too failed in it's duty (well, until he was about to crash anyway and then it seemed to work)

!
Fishier than a barrel full of fish with some fishy sauce added, if you ask me!