To add the second bolt, they would have to change out the rear subframe first. And to change the subframe they have to drop the exhaust, rear driveshaft, and drop the subframe, then swap the suspension and rear diff over to the new subframe, then put it all back together. That's a lot of labor. If you were to pay out of pocket for a rear subframe swap, I can see the bill being around 3-4K. That is why I wouldn't put it past ford to try take the cheap way out.
Ford wouldn't outright admit they detuned them, they would claim something along the lines of they softened the torque output to put less strain on the rear diff. Or some similar story to cover their ass. 90% of the ST and Platinum owners would never notice the difference, but we would, and frankly we are the minority.
Honestly, it would be hard to prove they detuned them. I've personally seen a 10 hp difference on a chassis dyno on two back to back pulls with the same vehicle on the same day with no changes. Even if you managed to have a stock dyno run and went back after the recall to the same dyno, ford would claim it was the weather conditions that changed causing a lower reading.
Personally, I would recommend to wait it out and see what exactly they are going to do for this recall. If it's just a PCM update, PASS. But if there is also a rear subframe replacement, then maybe put it back to stock, take it in for the recall, then load your tune back on when you get it back. Even if you have to pay your tuner a Benjamin to update your tune after the recall, it's far cheaper than 3-4K for a rear subframe swap.