Priming is picking by height. Tobacco ripens from the ground up. Field crews take the lowest leaves first (volado), then the middle (seco, viso), then the crown (ligero). Each pass is a priming. The other method, stalk cutting, takes the whole plant at once and is more common on some filler crops than on delicate wrapper.
The point is that one plant is several products. Wrapper, binder, and the filler grades can all come off the same stalk if the leaf qualifies. Most of it will not qualify as wrapper.
Priming is farm language. It is how ligero leaf becomes a different ingredient from the leaf that sat in the dirt’s shade.