You are assuming that BMW is claiming that for marketing purposes but you are not offering any evidence to the contrary. So, how much weight will be transferred? Also, not all BMW's have 50/50? Some diesels are heavier in front, for obvious reasons, and than some 4cyl have actually 48/52% distribution.
Yes, I agree, not all BMWs have 50/50 weight distribution, that's why I said "many" BMWs have 50/50, not "all" in my post above.
Second, 50/50 is a marketing point. It's why you're repeating the phrase like a broken record player. BMW has brainwashed the masses about "50/50," which really is meaningless. And this ad solidifies the point of "50/50 weight distribution" being a marketing point. https://www.youtube.com/watch?v=qobu0pJPHPQhttps://www.youtube.com/watch?v=ajjgTNKz9m4
Third, how much weight will be "transferred?" That would obviously depend on how hard you're jamming the gas or brake pedal. If you have a high-enough power engine, and mash the gas, you can get the front wheels completely off the ground, even if the car is "50/50" at a stop. For the last time, what's more important than static weight distribution and "50/50" is mass distribution. You can make your car have "50/50 weight distribution" right now; just attach a 1 ton ballast to the front and rear bumpers of your car. Of course, that's a meaningless exercise. More relevant is the placement of the mass; hence the number of high-performance and supercars relying on mid-engine configurations more than anything else--getting the majority of the mass in the center of the car is ideal.
I would say modularity, particularly transverse applications are to "blame."
Why would a "modularity" force the timing chain to be on the rear in a longitudinal application? These two concepts are unreleated. BMW placed the timing components on the rear at the expense of added weight and mass for one simple reason: mass distribution. As a matter of fact, BMW had to sacrifice some weight savings to place the timing components on the rear of the engine. Additional sound insulation had to be added along the firewall to keep occupants from complaining about noise. In short, BMW prioritized mass distribution over weight savings. Their ads talk about "weight distribution," but the engineers are actually worried about mass distribution (and NVH). Moving the timing components to the front of the engine would have resulted in weight savings (less sound insulation needed) but would have resulted in a slightly worse mass distribution as now all the timing components (VANOS, chain, tensioners, pulleys) are toward the nose of the car.