Can my case really be that clinical?
Good question. It makes little sense. You obviously have a electronic or mechanical problem with your disks (a power surge probably being that it happened to all at the same time. But it's irrelevant for me to speculate). In any case their intent seem to be to replace the damaged parts with identical ones.
However, disks aren't such a bigot piece of hardware that can't take parts from other similar models in order to function well enough to move on to the data recovery process. More so because you are only interested on said data recovery (not on recovering the disks themselves... right?). So it's even more odd when they go to the point of requesting the disk to have been manufactured on the same factory despite the part number being the same. I find no explanation for that, other than them trying to cover themselves from any accidental damage finally rendering the recovery impossible.
I'm not sure who you are talking with to do this, but I'd probably suggest to go somewhere else. Go online and search for other options for data recovery. Good data recovery centers don't ask anything from their customers and take matters on their hands.
In any case, to answer your question directly no one in here will be able to provide you with a satisfactory answer, I think. Unless they happen to work on any of IBM's hardware departments. That's where I suggest you to go. Contact IBM directly with the information about those disks in your hand and explain to them the problem. They are your best hope for said exact same-everything these two data recovery centers are asking from you.
For Data recovery Centers in Europe, you can hardly miss with the folks at Ontrack. They have facilities a little across the whole continent as well as in North America, Asia and Oceania.
If the price isn't right for you, you can dig deeper and go to IPDRA (International Professional Data Recovery Association) and look at their directory.
Meanwhile, I have personally used DRC services in the past with a high satisfaction rate and fair price.