When I worked for a local coop, we would regularly spread 3 tons/acre of lime.Up here in the northland, that is a common practice for alfalfa fields. I can not think of a good reasontoleave lime in the soil surface. They may have suggested not to work it in so it neutralized the top of the soil profile, making look like your soil hada higher pH if you re-sampled. All lime and fertilizers need water to make them work and/or be available to plants. Mixing it in will give ithe lime a lot more soil to work with and neutralize more soil acidity faster. You could always grow blueberries, I wish I had a small plot with a pH of 4.7 to grow them!