The mash temps in the recipe are placed there for you to get the closest to the flavor and body of the beer as the recipe gave the original brewer. The lower the temp you mash, the higher the OG, the higher the temp of the mash the lower the OG but the higher the body of the beer. I found this out after several mashes. I couldn't figure out why my FG was often much higher than it should have been and why I could never reach the specified OG of a recipe. My Walmart purchased electronic temperature probe was 6 degrees low from what it showed. So when I thought I was mashing at 152, according to my temp probe, I was actually mashing at 158 where a lot of starches do not convert to sugar, thus I could not reach the recipe OG, even my iodine tests would never show complete conversion. After answering my suspicions of temp probe problems by buying a new temp gauge, (this time I bought a glass thermometer), I started mashing using the regular thermometer and VIOLA! I was reaching the recipe OG and fermenting down to FG of 1.000 or less.
Anyway, I digress.
IF you want the same body and flavor as the original brewer recipe then you use his mash temps. Otherwise if you want more or less body/alcohol, then you "do your own Thang."
Bye, and have a nice day.