Absolutely normal. When in neutral the main/output shaft is free to rotate in the speed gears. The speed gears are engaged with the cluster gear, which is engaged with the input shaft, which is engaged with the clutch disc. Foot off the clutch, engine off, none of these can rotate. As mentioned above the main shaft is free to rotate. When you put it in a gear, you are locking that gear to the main shaft. Since the gear can't rotate, the main shaft can no longer rotate. After I tighten down the clutch bolts I pull the alignment tool and reinstall it a couple of times in different positions to check for concentricity.