I just explained how I got them loose. With the T55 if messed up and if have to heat use wax to assist. In your opinion, this it has nothing to do with improper fitment. That is fine. I personally don't understand why you needed a video to explain just tap the head of the drain plug with a hammer. However, that is your choice to do so.

I totally disagree with the copper being the source of them being stuck. as they used copper washer on all differential drain plugs way back without issues( 1970's and 1980 trucks diffs, transmissions and Transfer). They are getting stuck due to lack of proper gear grease change intervals or being way over tightened in the past. As I have seen this occur for over 35 years from previous owners neglect. The fill plugs are known to stick with that gasket washer not being copper as its steel or aluminum. If your theory was correct, the fill plug would never stick and I seen many of folks have just as much issues with them along with drain plug in the front differential is why I base the copper is probably not the only cause of this seizing of the plugs.
Because, by making a video and sharing it on YouTube, people can find the information easier. How many people am I going to reach by posting it on this forum as opposed to posting it on YouTube? I guarantee I'm reaching exponentially more people via YouTube than on this dying forum platform. The video is also to give people a live demonstration of how well the technique works. Saying something works is fine, but there's no proof. I show people how well it works so it takes away the ability of people to distrust it as being a legit technique to use.
I have personally tightened these drain plugs many times and I have never overtightened them. I tightened them with very little force with a 3/8" ratchet and after 30,000 miles, that drain plug ain't budging with the same 3/8" ratchet I tightened it with. I would go to a 1/2" drive ratchet and it would still not budge. After applying heat or using the hammer technique, the thing would break loose with ease. With the same tightening force applied with the 3/8" ratchet for the fill plugs, I have never had a fill plug fight me coming out. Same goes for the transfer case fill and drain plugs and the rear differential fill and drain plugs. I tighten them with similar force and I can always break them free without a fight. Hmmm, I wonder what the difference could be? Could it be the copper washer? Using basic logic and deductive reasoning, I would say my theory holds water. I remember those copper washers from way back when, and I don't remember them having quite the surface area contact that these drain plug washers have and that might be the difference.
So, if the plug is not getting stuck to the copper washer, what is causing all the resistance of it breaking free? Are you trying to say it's the male threads of the plug getting locked into the female threads of the differential? So, your theory is they get stuck because of time or being overtightened. Ok, you're entitled to your opinion, but I know 100% based off my experience you're dead wrong. The problem with the front differential drain plugs becoming impossibly stuck is well-documented. If you did social media, which I sort of doubt you do, you would see the numerous posts on Toyota Facebook groups of people talking about this issue. Almost nobody strips the fill plug, but tons of guys have stripped the drain plug.
Now remember what happened last time when you kept coming at me and I didn't back down. You quit the forum for a while, remember? So, if you don't like how the conversation is going, I suggest you disengage, because this is my thread and I ain't going anywhere. If you post again, you're gonna get a response, and it might not be to your liking.