They are shìt.

Look nice but they are just driven via a timing belt to a straight thru spindle.
OK for engraving on wood or candles [ unlit ] but if you try to use these in anger the cutting forces of a decent cutter will force the drive backwards.

If you want a decent 4th axis then get a decent rotary table and fit a stepper motor to it. Because it has a 72:1 or 90:1 worm reduction it cannot be reverse driven.