I am not sure if this is what you guys are talking about or not. Anyways if you are talking about the angle the a-frame is to the ground in relation to the blade i might have some good information about Diamond.
On the Diamond push fram on the truck, there are 3 holes for the blade's a-frame to attach to ( this is on fisher too, even the minute-mounts, but it's hard to change the angle without quick pins). Anyways when the ground is frozen or we need good to scrape hard pack. I have the guys put the blade in the top hole, this puts the blade at a downward angle, so it wants to dig into the snow, lawn, gravel, or anything else unfrozen.
In the start of the reason, most truck use the middle hole, the blade is about level scrapes well but not as good as the top hole. Some trucks use the bottom hole, the drivers make the call, based on their route.
This way lawn and gravel aren't dug up as much. The middle of the season when everything is frozen, all trucks run with their blades in the top hole, which works very well.
In the spring like the two storms we had in march where everything was unfrozen. I think almost every truck ran their blades in the bottom hole. Here the cutting edge still makes contact with the ground, but less of a downard force is applied to the blade, so less damage is done to unfrozen surfaces.
I think Diamond is the only plow company that allows you to change the angle of the a-frame with quick pins. I know it can be done with a fisher but isn't easy.
Geoff