On the 528's my money is on this being a purposeful programming for fuel economy in D particularly since in DS there is no lag. At least that's how it seems with mine.
My Enclave had a similar MPG minded programming that created what felt like dead spots when accelerating. After a reprogram the dead spots went away and the SA warned it may decrease fuel economy, which I didn't care about (it's an 8 passenger vehicle...fuel economy isn't at the top of the list for this particular vehicle).
2013 335i Sport Line | Glacier Silver Metallic w/Black Leatherette & red highlight, Sport auto trans, Navi, Rear camera & PDC
2011 528i | Alpine White w/Black interior w/Anthracite, Sport Package, Premium Package 1, USB/iPod, Park Distance Control, Navigation
2008 535i (Buyback)