I watched part of one of her videos on using that ruler.
Her method of attaching rectangles to the sides of a square and trimming them down - seems cumbersome - and wasteful of fabric - to me.
The ruler also looks like something I would have to pay close attention to while using it. Maybe I would put tape on the "where I should line it up" so that I would remember my "target spot".
I have learned to make "test units" before cutting a zillion pieces - especially where/when triangles are involved. Sometimes cutting that triangle 1/16 inch larger (or smaller) makes the difference from not fitting to fitting almost fitting perfectly. (In my world - "perfect" is a word that is right up there with "always" and "never" - just another of my quirks - it happens occasionally, but not often)