Relevant question, but generally a non-issue in practice. This is because enlarging lenses are typically fast and used fairly wide open. So adjusting down just one stop won't make a radical difference in depth of field as far as viewing grain is concerned. But even with slower process lenses any such issues can be detected using a high-quality magnifier.
I take it you mean depth of focus and not depth of field, but it still means you are still trying to judge focus in a wider depth of focus.