Dan,
Many consider "washboarding" do be a desireable feature. So in this case it didn't come from "improper" use of a scraper or burnisher. I realize this is a personal preference and I would speculate that any washboarding on original guns was a consequence of materials and production techniques rather than a feature that was desired or sought after.
On some highly figured wood its quite difficult to avoid this all together. You can of course bridge teh figure while scraping and burnishing, but sometimes the shape of the stock makes this difficult. So my take is that with some wood and extensive use of a scraper in a workmanlike manner, some washbarding is going to be a consequence.
From a modern personal perspective, I often find surface texture such as that being discussed to be appealing. A surface with some texture is a bit more complex and seems to create more visual interest for me. Now don't get me wrong, I've made more guns finished flat and smooth than otherwise, but I do beleive that a textured surface showing some tool marks can be appealing. The key to this in my view is recoginizing that these tool marks are a consequence of tools and speed of work, rather than a desirable feature. Some work I've seen today seems to have marks that appear heavy, very deliberate and calculated rather than a consequence of working methods. From the view of toolmarks being a consequence, a perfect surface is the goal. It's the goal, but materials, tools and time constraints make this unobtainable. If tool marks are deliberatly indluded the results tend to be different in my view.
Jim