Lou, I am with you and Lee on this, if I were to make a poplar box with a cherry lid, I would want to make the base out of cherry as well. The base has to/should be glued to the box when it is tuned, I am not going into the specifics as to why that is a general rule, except to say,trade secrets,lol. Some times the plan is to build a box in a certain comb, say osage over butternut. The box is built and then it doesn't want to play with the woods chosen,osage paddle, it has to be onery, and will only play with a walnut, purpleheart or zebra wood paddle,just for example. This is one reason you might see this, otherwise it is just a choice made by a call maker or customer.