If a bolt is REAL loose, the improvemnt may be demonstrable. In most cases, it is not.
Taking a Remington action as a "for instance", the availability of reasonably priced replacement bolts makes the practice questionable if you are paying for it.
On a Savage, the trigger/ striker design minmizes the deflection of the bolt by the sear contact so a sloppy bolt is less a problem.
For what it may be worth; on a good shooting 40x in 6 PPC, bushing the bolt was good for about a .040 moa improvement in vertical dispersion. On a Winchester M70 in 6.5x55, I can't honestly say it made any difference at all. Regards, Bill.