To me, the virtually straight across break to me looks like dry rot, or the wood being too dry. Maybe length wouldn't have mattered in this case. However, I would agree with your first instincts that it coulda been a couple of inches longer. Draw length at 30, times 2 equals 60 + 10 inch stiff handle totals 70". Basic rule of thumb. Being backed, you might have gotten away with the couple less inches. Osage selfbow might be able to take it but I'm not so sure about the maple board. Just my two cents...