Again, I have different information than you...
I know that IWC has steadfastedly refused to change the back on any CFI. There was one person who order
ed the watch and was unhappy with it from the day he got it, and repeatedly requested that be done. IWC refused and refused in a few other cases.
There was one --and to my knowledge only one-- watch which left the factory without engraving on the back. That watch involved a special story, involving someone who was mortally ill and couldn't decide which son should inherit the watch (as you might guess that watch subsequently was sold by the heir, and then was resold again and perhaps a third time). It may be that one watch you've seen and identified twice.
It also is possible, at least in theory, that a CFI owner bought, relatively inexpensively, a second regular 3227, and changed backs, in order
to sell the one with the special dial. I doubt that has occurred, but some people do some strange things for money.
Finally, there has been close to 100% changeover in people at the factory who were involved in the CFI project. As such, I can't guarantee that the policy about changes to the model hasn't changed.
In all events, your question seems to imply that because you claim to know of two such watches (which may or may not be the case) that there are many others, and therefore implies that there may not be much meaning to the ownership experience. I say "bull". I know of virtually every English forum CFI owner, I know two weren't happy --and to me a 96% rating is pretty good.