Excellent research!
This has been my position from the start. It is rare for topical treatments to work effectively systematically. LittleLinda brought up the issue of nicotine patches; it occurred to me while going to bed that in the case of the patch working systematically the patient is already saturated with nicotine; you can smell it on a smoker. The nicotine in the patch is intended to replace smoked tobacco as a source of nicotine to help avoid smoking hazards involved in the addiction. Using an Ivermectin patch, so to speak, would seemingly fail since the patient's body would not already be saturated with Ivermectin.
Either of those are based upon solubility and permeability. If you stick an Organic Vapor Meter (OVM) tube in your mouth it will read a low but probably non zero level. If you stick a few fingers in a bowl of acetone while doing that it will show up nearly instantly...