tallchick

So I finally finished getting everything together and I just have the borders. The instructions say to sew the first border 1/4in away from the points (that I get) then trim away the excess and complete this process on each side. Is there a reason to do it this way rather than trim then add the border? Is it because of bias? I’m all for learning but have never heard of this one before.
I always cut the borders last, after I take my own measurements of the completed top. And in this case the border calls for dark blue inner then green then dark blue, all in the same width. I always sew the strips together to make one unit as I find it easier.
I really would like to just trim and add my borders, but not if it’s going to cause a lot of bias. Just looking for advice as I’d really like to get this one done this weekend so I can move on.