Be interesting to hear what people say, but it is worth noting that if the advice to seal comes from the US, they tend to have a much harsher climate for wood products. Summers can be very humid, or in some places brutally hot and dry, while winters in other places are crazy dry. I have seen multiple examples of wood products which were quite happy for years in the UK shrink badly and crack when taken to the US (New York and western Kentucky).
I have stuff that I carved in lime, yew, birch, beech and box that I may have oiled, lightly waxed, or done nothing to, and all have been fine here without varnish sealing, although most were seasoned before working, or were cut green so they didn't include the centre of the tree.