Clutching at straws or something important?
good question. i've adopted the practise for some time now. i'm now not sure if it makes a significant difference. i've not carried out a like for like comparison. when i made my last base (the KC) i made my current spec base at the same time. the initial water (as a proportion of the onion volume) was 75% for the KC and 20% for my current spec base. the bases are quite different in terms of taste but there was no discernable difference in sweetness.
i still prefer the lower initial volume method but can't put my finger on why or even be sure that there is a difference. Clearly both are BIR practise so i guess there must be no difference in the end result.