Following the post above, I can now see that it was me that was inadvertently quadrisecting the bottom left corner. I also failed to recognise that with the very first fold defining the angle to be trisected, you can create a pair of angles in any size ratio you want, not just 1:3 due to some strange property of folded paper, which is what I was vaguely thinking. I did it again with a better understanding, with the correctly interpreted results this time. My apologies.