Some of the "rules" are only meaningful when mathematics are applied. Like when working with triangles, the way you measure 1/4 inch seams help you (or should help you) get the tip of the triangle to be at the edge of the seam. Also, if you participate in a block exchange, the final size matters. Many machines have a 1/4 inch foot but not a 1/3 inch one, and when following a pattern, the measurements are made so that if you use a 1/4 inch, you end up with certain size block. Is up to you to change all that and do your own thing, but in some blocks you may not necessarily like the final result. In the end, is your quilt and your fabric. Just have fun with it.