I also am approaching my Grade 2 (aus) and have broached this same subject with my CFI.
We sat down and read the relevant para's and decided that NO....it does not have to be 200 ab-initio hours.
250 total instruction.
50 x-country
200 anything else.
which means that you don't neccesarily have to be a snr G3!!!...as ther is no longer a stipulation on ab-initio hours!!!
Going thru my logbook, I breathed a sigh of relief...as I could now count Night-circuits/nav's...Refresher flights, endorsements etc.
My CFI says he will be happy to sign off on the above...
good luck with yours!