If the 9 patch pieces and the 4 patch are the same size, this is a pattern that never should work out. I suspect the reason it does is the very small size - the amount the pieces are out is hidden by the level of accuracy possible at that size.
For those interested in the math - you want a 9 patch equal to a 4-patch square-in-a-square. If I am seeing the pattern correct that means that the length of 3 of the small blocks (the size of the 9 patch) has to equal the diagonal length of 2 of the small blocks (in the 4-patch). But, math tells me the 9-patch has a size of 3x (3 times the strip width). And the 4-patch has a size of 2.83 times the strip time (2 * square root 2). Doesn't matter what your strip width is - the sizes won't match.
Your 4-patch strips need to be 1.06 times the size of your 9-patch strips. As I said - negligible when the strip is less than an inch wide. At 1.5" for the 9-patch, the 4-patch should be 1 and 1/16 inch. At 2" for the 9-patch, the 4-patch should be 2 1/8.