Wow. I watched that, and then the video utub gave me next (grr, can't post links yet: 'ender 3, cr-10 - hotend ptfe fix' by CHEP

Seems to make sense that a plug like that would impeded filament flow and cause the kinds of issues I'm seeing. So I guess I gotta start looking for screws to take that all apart and maybe I'll find a plug in there too?

Easiest fix is to just push the tube in further? Maybe remove the nozzle, push the tube down into the nozzle threads, and then let the nozzle push the tube back up when I screw it in?

There's also the little washer designed by OneBadMarine mentioned in the 2nd video (thingiverse thing:3203831), that seems easy to try as well