Just my two cents. My brother and I have carried and read the (mini) version of this book literally everywhere for many years so I guess this has shaped the way I view J.L.Ws tome as opposed to a quick read through and storing it back on a bookshelf.
My view is that J.W didnt wish to mislead civvies that his manual represents the skill set of the SAS. Probably only 5% max. It is only a brief outline of the survival component only, and I reckon he imparted truck loads more detail than a book ever could.
Ive been attempting to use his survival tin (plus my additions) and always found it useful and reassuring. My reading is that J.W. never intended for the tin to be placed in your back pack the assumption being you could accidentally lose it. Then what? It would be in a trouser pocket say. Re The question about the survival pouch. It seems J.W.s intention was for these bulkier items stove/mess tin etc to be carried in a belt pouch with no doubling up in main pack. (Weight restriction re hundreds of rounds of ammo, claymore mines, minimi, radio, kitchen sink -what have you) Now if you lose your S.Pouch you still have shelter,fire,water,food at least partly nailed (the tin being on your person.)
My reading is that he intended the user to customize their S.K E.g. I also carry at least one lighter plus 2 pieces of rubber a la Ray Mears (burns fiercely for some time.) But I dont have a flare gun. (Maybe I should!)
This only my understanding of his manual fellow bushcrafters and I welcome alternative interpretation and implementation of J.Ws great system sos I can make any adjustments.