To be honest, it seems to me you are beginning to over complicate things. Stef didn’t say ‘false fat’ she said “…The weight they gain in captivity is quick due to all the free food and ‘false’….”. I took that to refer to a rehabilitated hog being likely to very quickly lose the weight on release. You might be interested in https://www.britishhedgehogs.org.uk/pdf/Hibernation-Weight.pdf
I, for one, appreciate, and think we on the forum are very lucky, that an experienced rehabilitator like Stef, gives us the time and patience to pass on some of her knowledge – particularly when she must be very busy at this time of year with large numbers of under-weight hoglets etc. This sort of information – stemming as it does from actual experience over a period of time, is invaluable and we can all learn from it. I certainly have.
I hope you find you are also able to learn from Stef’s advice and that the three hoglets safely survive the winter. I admire you for trying to help the little ones. Good luck.