Lathe tool height gauge - video

Lathe tool height gauge. By AlwaysSunnyintheShop. 21:02 video:

https://www.youtube.com/watch?v=mz-a8WANrzc

At 4:27 you have the height gauge sitting on the carriage (saddle) set for center of work piece, but in use you have the height tool sitting on the ways. Did I miss something?