well i couldnt tell you about flex because i have never had them straight. It does make sense though. Straight up and down should dampen more on the street because it travels mainly up and down(equal on both sides) over speed bumps pot holes etc. At a angle like the pic should let it flex more because while wheeling the axle is never really moving up and down equally. On tires moves up and one moves down. With them straight when one tire moves up they tend to bind. Not really good at explaining. Someone can probably explain it more clearly than i can.
