Not sure I am understanding the difficulty.
Are you aware that this pattern uses the Easy Angle ruler? This ruler nips off the 1/4" dog ear like this:
http://www.joscountryjunction.com/ha...asy-angle-way/ which is why you can use 2.5" strips of fabric instead of 2-7/8" strips of fabric.
The center square is 2" finished. You join a 4.5" strip to each side of a 2.5" strip, then subcut these to 2.5" inches wide. Meanwhile, you have joined two bear claws with a 2.5" wide strip in-between them to create a 2" finished strip in-between the two claws. The 2" finished center square corresponds to the 2" finished "sashing" strips separating the four claws.
I am not seeing a problem with the measurements in this pattern.