This may sound crazy but I had a thorn in the sidewall of a bias ply 13.6x 24 rear tire that turned out to be tube type which i found out way after making a repair. I got a new, gooey stick of packing, and opened a new tube of cement. Did the hole cleanout and ran the patch. So far so good.
My guess is that the tube has been in the tire for a long time and essentially vulcanized (somewhat) itself to the tire such that you have a solid sandwich. I know this happens from trying to pull tubes out of farm tires that have been in there for a long time. So, that being the case, and the fact that the tire was aired up, keeping the tube against the tire, it accepted the plug patch just like it were a tubeless.
Try it. You may win and surely worth the gamble vs tearing down something like that tire alone.