Looks to me like it's a fixed pinion with no on the fly adjustment while traveling, this is a bad idea to me because it doesn't account for any deviance over the racks length so will bind in places and wear quicker.
Also if something like a decent size chip gets between rack and pinion it will potentially jam up or if traveling slow with high torque do damage as the pinion will try to continue on it's way eating it in the process, something will have to bend or move and chances are it will be the pinion shaft or belt will snap.??? . . .Either way something bust's.!!

Yes even with on the fly adjustment way if something gets stuck between R&P it's going to jump teeth and lose position but no damge will be done to the machine.!!

Another thing I don't like is the fact the belt or what ever he use's for reduction is on the inside in the firing line.!!. . . . not good Idea IMO.!

Like those massive 35mm rails and flanged carriages thou, Shame he's attached it to what looks like a tall 15mm plate gantry side.!!! . . Would like to see the whole thing.