Exterior Painting and a Strata By Law for an extension

Good Morning,

I have already posted a few months ago which I cannot find, NSW Self managed town houses, and quotes for exterior painting and an extension and a strata by law. One of the units extended their unit, and a strata by law was passed that the owner are responsible for all aspects of their extension, however that particular owner is adamant and aggressive to me that with the painting quotes I am sourcing that we should take into consideration the original façade of his unit which is now inside is unit into the quote, I am saying that his is responsible for his extension and not the strata, and why we would strata take into consideration the previous building footprint. Any information would be appreciated.