Re: sealing butcherblock
Problem being that mineral oil evaporates, leaving the bottom bare. Mineral oil isn't waterproof anyway, so it's the same as no finish at all. In any case the bottom and top will be equal, but they may not have equal inputs of moisture; DW's put off a lot of steam.
I used salad bowl finish on my butcher block tabletop, it's a very thin food-safe varnish; with tabletop use 4 coats has held up pretty well for 6 years plus. Of course, I don't cut or chop on it.
Remove not the ancient landmark, which your fathers have set.