Just cut a 200 x 200 mm square. The X-axis is 198.6mm and the Y-axis is 196.1. Again, the diagonals (277.8mm) are exactly the same (at least within my ability to measure them) so it is cutting square, just loosing distances along the axes.
I also cut two circles which both came out circular. The 50 mm circle came out at 48.7 mm and the 100 mm circle was 98.7 mm. I cut a second set and the two circles each matched their respective other circle exactly so the MPCNC is cutting consistently, just of by about 1.3 mm in 20 cm