If bowing of the entire counter is forcing the center apart, -maybe- you could stop it (or possibly correct it somewhat) by screwing in strips of some non-warping material (wood maybe, metal might be better, like beefy aluminum angle) at intervals underneath the counter. Orient them perpendicular to the direction of the butcher block strips. Put screws in every few inches.

It was fear of this warpage happening that when I redid our kitchen with butcher block counters, I chose a drop-in/overmount apron front stainless sink. Has like a 3” wide lip all around on top of the counter, and is thin enough (roughly 1/16”) that once I put a bead of silicon at the edge, I can still easily rake crap off the counter right into the sink. Faucet, etc is all mounted on the sink, so less water exposure. About the worse thing so far has been some surface crud on the wood between the back lip and the wall.