This is a simple matter of the action being warped...as all Savage actions are to some extent as a result of the heat treating process. Savage only heat treats the bridges of the action, and in the rather quick heating and quenching process the action will warp in the middle where the magazine and ejection ports are due to their being less material there. On most actions the warpage isn't enough to worry about or cause problems as it can easily be dealt with via scope adjustment and/or adjustable mounts, but occasionally there's one that warps to a greater degree and can't be remedied with such basic solutions.

Long actions are more prone to excessive warping as they have a longer port area which can multiply the degree of warpage due to it's longer length. As a result the rear bridge of the action may be high, low, left or right of the front bridge. The solution is to have a competent gunsmith straighten the action or fight with Savage in hopes of getting it replaced. I don't know what Savage's tolerances are for "acceptable warpage", but I do know it's not something they routinely spot-check for during production.

As for the hand polishing excuse, that's only viable if it's an older gun made before 2003 or so. All Savage's built since then - blued or stainless - are polished on a rotisserie via a vibratory tumbler. Only those made earlier were hand polished on a buffing wheel. This hand polishing on the earlier models is also why so many of the flat's on the older flat-top actions weren't level.