Pinewood Derby Pot chuck?

Hello all, newbie here. Well I bought my first Mini lathe (7X12 grizzly) Really enjoying making bits and cutting on my first Pinewood derby wheels Note, (selling online to people for pro racing and Scout Nationals that allow lightened wheels). I've seen a few people use these Pot chucks. I understand somewhat but this one I've seen on you Tube doesn't have any cross cuts, I can only imagine it is cut with a Taper? And if you look closely (I've seen in another video) the center is a rod and will just pop out wheel).

so am I thinking this right?
1. pot chuck is probably 6-8 inches long
2. center cut out (to allow the rod to push the PWD wheel out)
3. Tapered to allow different size (heights)of wheels
4. Am I on track?

Thanks
Shawn

Looks like a Chinese lathe for making toys? If so...see you later