I tend to read the R-codes the same way, that open space requirements would still apply across the entirety of the lot. However, (and I know this is a Fremantle specific term) the FAQ from Fremantle seems to imply the opposite...
We're in the process of assessing development options for a ~1,300sqm, R25 lot in the City of Canning.
One of the options being assessed is a 3 lot battleaxe development with the front lot being green title and >450sqm to allow for a granny flat to be incorporated into the build.
This...