No disrespect to anyone...esp. not Tony...but on the face of it (in the absence of other explanations) that's bogus, IMO. My friend at Colonial Williamsburg makes historically correct, hand welted shoes with leather insoles as thin as 6 iron. And I've done dern near the same on some women's shoes I make--all hand welted.
And beyond that from the insole outward, gemming...which stands proud of the insole...and the concomitant thick cork make for at least as thick a profile as the virtual nothing that sits between a handwelted insole and the outsole.
PS...in my experience, toe spring is toe spring--it is set by the last and, like the heel height, more or less set in stone, as well. Nothing in the closing or bottoming techniques will alter or affect it.
I understand what you are saying as you can make a bespoke shoes as sleek as possible but that is because it is done by hand from start to finish with a lot of hand-manual manipulation. Now, I want this to turn into the same argument as on the gemming thread as it really is a waste of time. So please realize DW that I am not here to argue which is better, only to reiterate that they did an experiment and found that manufacturing the shoes BY MACHINE and using a thicker leather insole to have a proper holdfast did not give them the desired results for their end-product requirements. And I can concur that the shoes were not as attractive and did look off balance (as I saw the prototype in person).