DSVWGLI- Hmm... I sure wouldn't wash a 2' x 2' area (on a dirty vehicle) before rinsing out my wash medium, but then I wouldn't use a BHB without also using a foamgun either.
Assuming the BHB passed the CD test (my Montana ones did), the marring is coming from grinding dirt against the paint, either during the washing or when drying (gentle-enough BHBs, used by themselves, are likely to leave residual dirt, they require subsequent passes with a more aggressive wash medium after the "big stuff" has been BHBed off). Note that residual dirt that's too fine to see can still cause marring.
And note that I washed very carefully for *decades* (including years of single stage black lacquer) before I got my technique sorted out. [Shoot], it took dozens of washes with the foamgun before I got that technique just right. And heh heh, it's not like I'm a slow learner

Think about it..the dirt is highly abrasive (relative to the paint); just how *do* you move that abrasive dirt across the surface of the paint without causing marring? Washing without marring is simply *very* difficult.
Here's a basic test: how long is the marring? If most of the marring looks like light scratches that're *a few inches long* there's something fundamentally wrong with the wash technique. Any marring from the wash oughta be very short little scratches.
Eh, I'm not really thrilled with how parts of the above sound, hope I didn't sound all critical or anything
On the LSP issue:
The only time I've had marring that was only in the LSP (not the underlying paint) was with heavily layered KSG. And that marring was so slight as to be invisible under almost all condions.
The primary benefit of (some) LSPs is slickness and dirt-shedding. The dirt doesn't stick so it washes off easily.
Don't underestimate the importance of a great shampoo, one with great lubricity and encapsulation characteristics.