glenp, yes - its a lot to do with weight/balance. But off road on slower / slippery corners you can skimm your foot a bit to assist or save your washout with a dab in panic.
However the weight is transmitted to the bike where you are in contact with the bike. So sitting on the tank will give the front grip. Taking your foot off the peg will mean the weight is left to be transmitted to the bike via your ass and hands, which should be up front. Outside peg weighted to stop the slip. Taking your foot off the inside has the effect of weighting the outside one.
Its like standing on the scales with a 10kg weight in your hand. You still weigh 10kg with the 10kg weight held out or held in.
I did try using my foot to hold up my bike on road once. It didnt work, I just got my leg pulled backwards and nearly fell off the back of the bike.