Werner says this "should not" be used with Type III aluminum ladder. Does that mean absolutely not? If so, why not? Any way to make adjustments?

I believe the Type III aluminum ladders are made in 3 sections so you can reach greater heights than a 2 section extension ladder. These 3 section ladders also have bigger rungs. So you might have trouble installing the stabilizer on the rungs as well as controlling the ladder when extended. I use it on a 28ft fiberglass ladder and its a real challenge when you install the stabilizer on the top rung and then fully extend the ladder prior to leaning it onto the roof.