If you look at the Ferrari and Koenigsegg, they look very much like outlets, not inlets. I think that there are multiple effects in play here making it very much a 'package' design. First, venting radiator exhaust air, second brake cooling, third preventing high pressure build up to assist downforce, fourth shielding the front wheel from the direct approach of air such as in an open wheeled car. I think that is is very much a clever packaging of requirements to achieve what is absolutely necessary (e.g radiator cooling) without detriment to, and where possible improvement to other important features such as downforce. If we were able to look at each of these cars in detail, and drill down to understand how each one works, there would be some similarities in their approach, but significant differences too. My guess is that the design approach would range from a simplistic 'lets have some slots to let the air out' to a more ambitious 'let's spend some time analysing how we can do this to optimise brake cooling and downforce'.
