Actually this photoshop montage has not been done by me but by Bruno of chronomania at the time of the Jones release, with the aim of proving they were the same basis.At the time I disagreed (I still do), but I thought it was relevant to bring this (imperfect) montage here to show how close they are when you said there layout don't match (which I partially disagree with)..
But I agree with you that most savonette movement will likely have this same layout anyway.
On the other hand, and to be back to the initial topic, I think you think like me that such a similarity is highly unlikely in the case of a complex chronograph, and therefore I am waiting for the explanation that Nicolas will try to dig out on the 'history' behind the making of the JLC 751 with much anticipation.
Sorry to have a bit messed up with my initial message on the FP / JLC controversy with this slightly off-topic IWC montage. As Dje had brought the comparison, I wanted to express what my feeling was on that one, which is clearly not the same situation / not comparable with the chronograph case,