I bet you that if I cut the blocks to 84.7 mm they would do just fine. If they don't, you take a file to one of them.
And you have to do it like this with wood, anyway - because of imprecise saws, and moisture changes.
Yeah my point was every measurement system has some value you can’t easily divide into thirds. How you measure depends on your tolerances. I have no qualms using either system, but metric is a much better system in my opinion.