From my experience it isn’t burped - more like projectile vomiting. The big nozzles are designed to fill vertically from the top of a tank through a three inch opening, so they flow a lot and I guess they normally shut off as they should in a truck tank.
But with DP the nozzle is almost horizontal and when that large volume of fuel rapidly climbs the smaller fill pipe it can’t shut off the flow fast enough, so a good amount comes gushing out over the side and onto the ground.
A “Diesel Guard” would have to be about twice as wide and 2’ long, and you’d still leave a puddle on the ground, but its a good idea. I just shut the thing off when I hear the fuel start to come up the fill pipe. Also diesel doesn't hurt the paint, it just makes a mess and dirt sticks to it.