Very interesting - thanks!
I have to say that the Ingenieur is not my favourite of the IWC stable by a long chalk (just a personal taste thing) but there is no doubt it is an excellent watch.
I saw one post somewhere where the very good point "why should an in-house movement necessarily be any better than a bought-in alternative?" was made.
If you take a movement from ETA that has proven reliability and accuracy in the standard form and then re-engineer it to be even better, that seems a very sensible way to proceed.
A bit like taking say a Ford V8 and then having Carroll Shelby re-building it with top notch performance parts: the original was fine - but the Shelby is WAY better!