Protection is a relative term and there's lots to protect against besides abrasion.
Most marring is caused by abrasive stuff getting pressed against the paint. Even with wax/etc. on top of it, the abrasive stuff will "cut" through, cutting a channel in the paint. Paint is generally a lot tougher than wax, so sopething abrasive enough to scratch paint will also scratch through the wax.
It's *very* rare for a LSP to provide true, demonstrable abrasion resistance. I've only had it happen with *very* light abrasion on multiple (at least six) coats of KSG. As best I could tell, the extra-fine micromarring was only in the KSG, not in the paint. But that's the only example I can think of offhand and I've been doing this since the '70s.
Example: put some plastic wrap over a piece of soft wood- the wrap is the wax and the wood is the paint. Press against the plastic wrap with something dull like the handle of a spoon. You'll be able to dent/scratch/mar the wood without damaging the plastic wrap if you do it gently. Even if you tear the wrap, think of that as being a piece of grit cutting through your wax. The wrap was "protecting" the wood, just not (sufficiently) against that particular damage.
The trick is to wash so gently that the dirt doesn't get pressed against the paint that hard. If you do it right, the wax/etc. will offer sufficient protection. Big "if" though. IMO the best protection that most LSPs offer against marring is their slickness- the dirt can "slide off" or get floated off the surface without much pressure being applied.
