The Ultimate Line Winding System

When I looked at the pictures of the "Ultimate Line Winding System," it looked like it would work fine for baitcasting reels and fly casting reels, but I couldn't figure out why it wouldn't put another twist in the line every time the bail on a spinning reel rotated.  So I looked at a video which shows the winder in action, and the device which holds the reel of new line rotates every time the bail on the spinning reel rotates, which prevents the line from twisting.  Pretty nifty.

But I can't figure out what makes the device which holds the reel of new line rotate.  For those of you who have used the device to wind line onto spinning reels, what makes the device which holds the reel of new line rotate when you use the "Ultimate Line Winding System" to wind line onto a spinning reel?

The device that holds the spool of line is mounted on a couple of ball bearings. The combination of line tension and bail rotation is all the energy needed to rotate the spool. There is an "anti-rotation" thumb screw to lock that axle in place when spooling conventional/baitcast reels.

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