I have done the 10 min block a few times. enjoyed this.. I am a nut about dimensions.. was in the engineering world for a long time.. don't be too unhappy.. does not look like a mistake for a seam ripper.. ( have gone through seam rippers plenty in my sewing time)
Keep on working.. use the same size square material for all five squares. fold in half exactly and it all works out.. maybe pin as you go.. it might be from shifting fabric.
have perfect points.. but then.. I talk a whole lot of time.. I am just amazed of the idea to flip the fabric and Wwwahhh Laaah.. the things comes out ! Amazing.
Enjoy your block ! keep on making them.. :0)