I agree with the above. Try to get it nice and stable 1st with the least amount of deviation.
On the other hand, 1.2mm deviation over 40 inches is not very much. On a laminated neck, you could use the part of the wood where there is the least amount of deviation, or none at all.
One thing I learned in working with wood over the years is that every pass through a jointer, planer, table saw, rasp or any shaping tool releases some potential tension in the wood that could make it shift a little. The most important thing I look, above all, is grain.
You need straight grain with little runout for a neck. You cheat a little on a laminated neck but the basic rule still applies.