Not to mention that just because you have a 1/8 doesn't mean it is exactly 1/8. It could lean toward 1/7 or 1/9 depending on the machinery or the day it was made. It is almost never exact. But it should be close.
Add in environmental factors, as well as differences in powder, seating depth, primer, cases ...and there is a whole lot more influencing the performance than twist rate alone.
In my view, the goal is to stabilize and stabilize well (meaning even in cold weather shooting long distance) ...after that, don't worry about it. I don't think it is a big deal in performance unless you have some sort of super-match benchrest gun. These guys with space-guns shooting sub .2 moa all day long. They have this concern.