Second, you must understand that not all cars are created the same, so the internal structures, drivetrain location, engine configuration, etc, etc are different, so not all cars have the same space for clearence between engine and sheet metal, as the regulations ask.
Third, there is that small, little, insignificant detail called "grill design"
Is way more easier to disguise Audi grill for example, than BMW or Merc ones, and come with a more armonious or less bulky design. Not to talk about Porsche's lack of grill......
Allow me to call BS again, porsche, audi, merc, etc. all carry longitudinal engines, the Audi grill is massive compared to the bmw grill, yet they still found a way to nicely integrate it whether q5 or r8.
I will try one last time (bmw pics only as audi badge seems to cause confusion). Carefully study the m3 pics. There is no bonnet line, there is no badge, there are no grills, no bumpers, no fenders just a beautifully designed one-piece harmonious shape that is the m3. The bonnet line blends in with the lights/fenders/grilles/badge/bumper. The shape of the grills in turn blends with the bonnet. Every feature from the air vents to the mirrors via the creases on the bonnet works in synergy. Everything integrates well together. You can start from anywhere take a line and follow the whole car from start to end.
Now take a look at your beloved 5er. I see a car; sides, rear, top, bonnet, ok not good looking but innofensive. So far so good. Moving to the front. They managed to create a headlight shape which manages to look wrong from any side you look at it, drew a completely straight line connecting the two lights where the bonnet ends and slapped a generic one piece grille/bumper what ever that is which fares no resemblance to the rest of the car what so ever. The design doesn't flow one way or another. Shape of bonnet line is wrong, shape of lights is wrong, shape of grilles is wrong, the whole bumper is wrong. It looks like the front of the car was chopped clean off and then an aftermarked bumper attached, which seems to be already separating at the top. Only redeeming feature is if have a front end shunt it will takes weeks for others to notice as the front already had that caved in look.
Now there is only two things I can think of. 1) Either the bmw designers were incredibly lazy or 2) completely useless*
* ok not completely useless, they remember to put on the badge which is what matters the most it appears.
Where it all started (I think):
Now with the f30 looks like the took the easy way out, 5er rear (probably didn't have the jetta drawings on hand), e90 sides, generic front but then someone must have sat on the clay model's front by mistake. No other way to explain this: