I've heard the AlBooks are "counterweighted" ("countersprung"?) to raise with less effort, and rely less on friction than the previous PBooks. So I'm guessing the different feel is intentional. My PBG3 is stiff and I don't like it that way really. Plus, I think those stiff hinges become worn over time from the friction.
Now, if it's floppy enough to sag on it's own when you don't even touch it, that's not effortless, that's a problem!
Sadly, the ones I've seen on display were not set up to allow me to play with the angle.