Having now put 12k miles on my car I'm not sure I believe this to be a transitional feature. I have over the course of many commuting trips on the same highways switched between D and B mode to see if one outperforms the other, and always had the expectation that B would eventually prove superior. Surprisingly, D has always been the winner. I have not once found B to be better than D in terms of range even when I manually switch between D and B mid drive to take advantage of downhill sections of highways. The best I've ever gotten was basically a tie.
On the highways there is little difference and no need to use B mode, even if driving on mountains - If you have the cruise control set, the car will regen on the downhill slopes the same in D as it does in B. I much prefer B (obviously) but even I cannot find any advantage to it on the highways
I know there are many of you who will reject my notion that passengers widely prefer D mode over B since they don't sway back and forth like puppets hanging from strings! While it's not hard to compensate for B mode on open roads, driving in heavy traffic or dense urban areas means lots of unexpected deceleration and acceleration and the resultant head bobbing...and nauseated passengers.
In city driving and stop and go traffic is where B mode really shines. You can stay with the flow of traffic smoothly and never need to touch the brake pedal,
once you get the hang of it - When done properly (which it's becoming very evident that not everyone can do) it's
just as smooth in B as it is in D and easier (for some of us) to do because there's only one pedal to mess with. I've come to the conclusion that it's something you either have a knack for, or you don't . . . . and, I believe that's largely a factor of what you've been driving for the past many years
I actually think VW has a better idea with the D mode. It's much more user friendly and pleasant for anyone riding in the car. And range-wise it's either equal or better than driving in B mode for me.
D mode is always going to be easier to use and more natural for anyone who has exclusively driven ICE's with automatic transmissions, because that's what D mode is designed to emulate - They've gotta include a mode which makes driving this very different EV as close as possible to the cars you came from, or people aren't gonna like EV's . . . . period!
If on the other hand, you've exclusively driven manual transmission cars and going 100 to 150K on a set of brake pads is more or less normal for you, then you will probably adapt to using B mode much more quickly . . . . and you'll probably prefer it - You're already not used to doing too much with the brake pedal and engine braking has been something you've done very naturally for many, many years, whereas engine braking with automatic transmissions is pretty much non-existent