This is a great thread, thanks Eric for taking the time to do this and Mark for your extensive comments, I know you have been worried about burnout and I appreciate that you have remained active on this forum.
I have a few takeaways from all this. One comes from Mark's contention that this experiment is not valid because Star San is "cheating" by remaining on the surface longer (cheating is my word, not Mark's). Mark keeps alluding to the fact that the wort that is added to the fermenter will instantly wash it off and change the PH thusly making it ineffective. Fair enough but a fermenter is a very easy thing to clean thoroughly, I believe that washing and scrubbing with brewery cleansers that we all use (or soap and water for that matter) gets rid of enough of the microflora on its own to prevent infections and soaking in star san until wort is added keeps it that way. Since, as noted, Star San sticks to surfaces longer, its a good thing to have coating the surface of the fermenter wall above the wort level, keeping microbe growth in check until the krausen comes into contact with it before falling back into the beer. Also, wort that comes into contact with these surfaces should be getting a healthy pitch of the desired culture to overwhelm the small amount of microbes that survived, albeit in a weakened state.
I think the bigger problem is brewing equipment that is hard to wash: racking canes, tubing, spigots, bottling wands, air locks, kegging equipment etc. Its one reason I pour instead of rack my wort into the fermenter. These I currently soak in oxyclean and physically scrub what I can reach then soak in star san until use. This seems to do a good enough job based on no infections since using this method but they simply cannot be scrubbed thoroughly and should be replaced periodically. I wish I could soak them in alcohol but the volume needed is prohibitive. I do soak these in a bleach solution periodically and am considering quat tablets.