Yes, it didn't seem to you, this stand is neither comfortable nor accurate. The idea itself is not a bad idea, but the amount of backlash is simply unrealistically large.
There is a backlash in the guides (thanks to Ali), there is a backlash at the pivot point, and the biggest backlash is at the grinder's attachment point.

Therefore, the video was released so that people do not collect this. If such a structure is needed, then it is made of metal, with precise and reliable attachment and pivot points.