Really? Do you have any proof of that? I have loaded and a couple hundred HBWC bullets backwards and shot them into mud, putty and water bottles and never had a single bullet fragment or seperate. They were not very accurate and more likely than not the skirt would mash flat and not expand at all. I would never depend on them for SD load.
In theory if you load a HBWC with too hot of a charge the base could seperate from the solid part of the bullet. Thats with the bullet loaded point first. I have loaded up to 4.5grs of bullseye to see if I could get it to seperate but it never happened.
Proof? I did it in 1982. the same old story was around even before the internet! So after I got out of the Army my dad and I decided to try it. Loaded up some Speer swaged lead HBWC backwards, looked mean.... At 25 yards for each shot fired there were 2 holes in the target, one was clearly the main part key-holing. Same results at 15 yards.
Thats all the "Proof" I have. It is the same as the "WC is the ultimate secret for SD" . this crap resurrects itself every few years. There are all kinds of gimmick rounds out there, me I want a bullets that goes where I want it to at any reasonable distance and penetrates deep - every-time. And no I am not going to produce a you-tube video, and I don't have any sworn depositions.
You want to load a round that is an urban legend into your gun to protect yourself when rounds with 2 to 3 times the energy have failed to stop attacks, have fun.