You do not need a 20MOA base to zero it at 200 yards. A 20MOA base (or any base with extra "elevation" built in) cants your scope very slightly downward which gives you more room for adjustment when dialing in your zero for those long distances where a lot of adjustment is needed.

For example, my dad is shooting a 300WM. He wants to shoot 1500yrds with it. He does the math and finds out that he needs 30 MOA of adjustment (this is all hypothetical I'm completely guestimating). He goes to dial in the 30MOA of elevation adjustment needed for the drop at 1500yrds and his scope "bottoms out" or runs out of adjustment - my dad cusses and throws a fit and blames the scope and me for talking him into buying it. If he'd used a 20MOA mount, he would've had 20MOA more adjustment until he bottomed out because it would've canted his scope slightly downward to make up for all that adjustment.