If it were a brake (only part I have experience with), BMW would ring up the sales guy at the supplier and give a list of requirements. They then have a number of meetings until an offer is made. This is usually in the form of "standard part A costs £x but doesn't meet your spec here, here and here. standard part B cost £y and is over specced here and here, non-standard part C is exactly what you want and costs £Z plus £ABCD for tooling". There is then a stand up fight between the buyer who wants C at price A and the engineers who just want C. They eventually buy A or B on the understanding C can be rushed in if it fails any testing .

The mistake with the fork could be:

1. BMW were wrong about some aspect of weight, vibration etc. and didn't test it.
2. BMW sales told BMW engineering this is a 100% road bike for old ladies and no one will ever ride it off road, wheelie it, put more than 10,000 miles on it and cost is hyper sensitive.
3. Showa have a genuine quality of casting issue and switched supplier, the new one only taking the job if they could change the profile.
4. There is something genuinely unexpected on this bike.

If it's 4 and Showa did their job they will have pointed out that for example the hole for the ABS sensor isn't something that's been done with this fork before. BMW should then have done a lifetime test regadless of cost and time.

I won't name names, but I know of a brake that was used by four different OEM's. The brake supplier told them all the known test requirements and they all did it. Years later one of them had an issue no one in the world had ever seen before because their vehicle heated and cooled the brakes in a certain way and had a different electrical charge across the axles. Large universities couldn't reproduce this off the vehicle. There could be no blame to the original design team for not knowing this might happen IMHO. The team that ran the service action and designed the retrofit part acted in a responsible way regardless even though part of the new design were a belt and braces approach based on how one material was different to another. The testing on the solution was a massive expense but showed the comittment to the safety of the user. BMW's simple solution of making it bigger could suggest they are in this sort of area, but we don't know.

The lack of a service reaction once the issue is known is the only thing we can lay at BMW's door until we know more IMHO.

Andy