Yep, that's almost right. The third point of support is the rocker ball/nut. On factory stock Pontiac rockers and studs, the factory specifies that the rocker ball nuts be torqued down to 20 lb.ft. (they bottom on the shoulders of the factory "bottleneck" studs). If you're running an aftermarket adjustable valve train with poly-locks, then the adjustment procedure is different but the rocker pivot point still provides that third point of support that controls the upward force of either the pushrod or the valve spring.