At lift off the bow effectively becomes longer which causes that deflection in the graph line,
In a recurve with string contact or bridges, the bow acts like a short, stout bow headed for a high, stacky draw weight with poor leverage. It acts like a short, overdrawn straight limb bow. At some point of the draw, the string lifts and begins exercising its leverage against the tip of the bow, instead of where it was touching the bow. The bow is now 8" longer than it was, or whatever. Suddenly, it is headed for a much lower draw weight, has tons of leverage, and is already AT much of it's total draw weight.
I DON'T prefer tiny, tight radius static recurves that go to 90 degrees, but they work great on wooden bows. They lift off slowly, just creeping the string up the curves I like deflexed bows (for stability and to reduce belly strain) with bigger recurves that hit 60 degrees or so. They have really high string tension before you even start to draw, and the bow gets longer and the leverage increases, starting after just a few inches of draw. I often add string bridges because I can lower strain on the wood by using them, and they make the recurves act like they have more angle than they do.
