Eh - guys have killed game for over a hundred years with 100yard zeroes. I personally only use 3" for my MPBR calculations, as I've never been comfortable being 2.5" PLUS HALF OF MY GROUP SIZE off of my target. A +/-2.5" MPBR at 300yrds with a 1moa rifle means my impact might find itself 4" under my aiming point - which might mean I blow through below the heart and lungs, instead of hitting them.

I do zero my optics for longer ranges, typically, to allow me to minimize my corrections, but I DO hold for elevation/range when I make a longer shot. It's not so difficult to estimate 2-3" of hold over out to 300yrds (~4x thickness of your crosshairs), which lets me take out the slack in that 4" above, bringing my "miss margin" down to only 1.5" instead of 4". I also hold under for closer shots, although it's less critical to do so, since 1moa at closer ranges is incrementally smaller.

And of course, if you're hunting golf balls, a +/-2.5" MPBR tolerance doesn't work. The OP didn't say anything about hunting, so there's no way to know what his tolerance margin might be.

So for the OP's sake in this learning process, MPBR is a great philosophy, but it's not without it's own faults and it isn't a free lunch.