Absolute rubbish! I wouldn't dream of trying to carry what I routinely put in just one pannier.
In fact I still do it - regularly (as does my wife.) I'm on my second or third set of panniers (over 45 years) and have used them for touring and shopping - including daily up and over hills in Bristol when I was a lot younger!
I said, earlier in this thread I think, that carrying heavy loads off your arms and shoulders is mad - and the reason why the yoke was invented and is still in use world-wide. The Viet Minh defeated the Yanks by using bikes -even without tyres - as their load-shifters. Go back to Arthur Ransome and see the children call their bikes their "dromedaries!"
I’d like to see you get bog roll (if you can find it!) into a pannier. Or kitchen roll. I also wonder how it all fares with the bumps and knocks.
Or the larger cereal boxes (which are far cheaper).
I think your “careful packing” and comments on cycling/pannier history illustrates this is a niche method suited to someone who is really into cycling, panniers and so on.It really doesnt have any relevance to the wider public.
As I said, I have panniers and have done masses of cycling plus am fit. I still wouldn’t do this as I think walking is easier.