with the dist installed of course, if you barely twist the rotor back & forth, not enough to be stretching the springs at all (& the spring tension is there only when twisting in one direction, CW on a SB), then any slop is in the lower tang. Most dists have "some" but you do want it as close to zero as possible.
Yes I'm mimicking an installed situation by grabbing the bottom half of the distributor shaft with my hand and holding it steady, same as it would be installed in the engine, and then grabbing the top part of the shaft where the rotor goes and twisting it I can get it to move a little bit and it would retract just like it was spring loaded. So it makes sense that it is the advance mechanism and springs causing that.
