Foolish question here from an old-timer. Does the second level of horizontal lumber (let's call it shelving) near the floor provide the same amount of sturdiness to the benchwork construction as the old diagonal bracing that used to be placed in the corners and between the legs? I kind of worry about somebody leaning on an end of your benchwork and watching the whole thing collapse toward the other side. Didn't Westcott recommend gussets or diagonal bracing?
Yes it does. Westcott recommended diagonal bracing because he used 1x4 and 1x2 lumber. Whenever you connect a a rectangular frame with a solid sheet of plywood, it constitutes diagonal bracing on all four corners. I can assure you leaning on an end of my bench work will not cause anything to collapse. The bench work will get a 5/8 inch plywood top as well which further strengthens it.