Well, the advancer shaft is this, it screws into the end of the crankshaft:
Onto this mounts the advancer assembly, then the large "nut" and then the smaller nut that holds it all in place:
It's just fine to spin the motor over with the advancer assembly removed, to check the runout of the shaft as shown in the video.
The key lesson here is that the large "nut" is really a cast metal shape that is somewhat thin where it engages the "ears" on the advancer assembly, and all of this is mounted on a fairly thin shaft, so it's important not to hulk out on it when turning the motor, or you can bend or break something.
The kick starter is not at a 1:1 ratio to the crankshaft, as it's geared to the clutch basket, which then turns the primary transmission shaft, which then spins the crankshaft via the primary chains. With all that i find it annoying to turn the motor over that way, and if you go past your mark accidentally then you have to make a complete revolution to get lined up again. I find it easier to sneak up on things slowly with the wrench on the "nut".
mystic_1