I think that you are misguided if you think that you are safe flying IFR without as a minimum complying with Annex 6.
Bookwork made no claim was to what was safe. He simply said that you were incorrect to claim that IMC holders and IR holders had different legal requirements regarding fuel. He's made that point pretty clear. IMC holder and IR holder have the same requirements, for domestic flight. IMC holders can't make international flights.
Your argument about only applying to international navigation does not wash because if I am holding at a UK aerodrome I am on an international flight and the UK Government assures me through Annex 6 and the differences filed that I will not have my hold time extended by a sequence of local pilots having to jump ahead of me in the sequence because they do not bother to carry reserves or diversion fuel.
On the contrary. It's your argument that does not wash, becuase that person in the hold could just as easily be an IR holder. The IR holder on a domestic flight, is operating to the same rules as the IMC holder on a domestic flight.
dp