All hot water tanks need some amount of hysteresis in the controls to keep from short-cycling, since longer burns increases average efficiency. But a hysteresis of 17F seems excessive for a 50 gallon tank- that's over 400lbs of water, quite a decent amount of thermal mass even for the 40KBTU/hr-output burner versions. (A 17 degree rise would be about a 10 minute, minimum burn.)
But if that's how they designed it, so be it. If you bumped the t-stat 130F it would only drop off to 113F before re-firing, which is still plenty hot for showers, even for filling cast-iron tubs.