I would go by this mantra: "scrape first for alignment, then for bearing and flake for lubrication, not for decoration".
My interpretation of the problem is the following: if you need to rely on scraping also per lubrication (e.g. where it is practically impossible to flake), it's very important that your scraping marks are rather deep.
Another advantage of having deep scraping marks on a measuring/spotting tool is that they resist more wear, that is more time before you need to re-scrape it (if I recall correctly, Richard mentioned that they used to scraper their straightedges with 0.5 thousands deep marks in the final passes to improve the durability).
A characteristic of shallow scraping, which could be either an advantage or a disadvantage, depending upon the cases is that there is no much volume for air and fluids to be displaced.
Personally, I prefer to keep my scraping fairly deep in everything I scrape.
Paolo