By the way, clearly when they say: "It was designed to be like that" - this is absolutely true, they have produced the undertray they (mis)designed.
The issue is that the design is bad and proves to be a failure in practice for many people and they need to address it - which is normal, many parts get redesigned on every car for every model year, to improve them and cut costs.
They've decided not to redesign it, and I think the only way we can change that is to constantly raise the issue with dealers and push for a fix.
So, even though I don't get exercised by this issue, many people do, so I am going to raise this with my dealer and I urge others to also.