Section 245 is the offence of administering a noxious substance to a person. In the Carter ruling, the Supreme Court did not identify this offence as being core to the prohibition against physician-assisted suicide. This offence has not been struck down.
It is an offence that is extremely unlikely to ever be charged in the context of medical assistance in dying. Nonetheless, we consider that out of an abundance of caution, because technically it might be an offence that could be legally applicable in the context of medical assistance in dying, a basic set of exemptions were put in to give certainty that also this offence should not be charged when a person has engaged in medical assistance in dying in conformity with the rules.
But it's extremely unlikely that this is an offence that would ever be a live issue in such a case.