As I said in the original posting this question (more or less) has been discussed on other NodeMCU sites, with conflicting answers.
Apparently on some NodeMCU boards there is a diode in the design that is supposed to prevent power feeding back from the VIN pin back thru to the USB port and then back into the attached PC (or in my case MacBook Pro). The VIN pin is listed as having a voltage input in the range of 5-12vdc, so I’m thinking that the diode may have issues dealing with voltages in the higher range. But, I don’t want to take a chance and damage my MacBook. So, I’m trying to completely avoid any NodeMCU board differences and simply make a “powerless” USB cable that avoids the issue entirely and still allows me to upload code and watch the serial monitor, with the board powered via the VIN pin (at 5vdc).
So, rather than asking “why do I believe that” do you have feedback on my actual question? Not offended by your question at all, just want to get feedback on what I’m actually asking. Hope that makes sense…