An interesting question.
The words '...shall be granted...' in the Act suggest that having shown (to different degrees for SGC and FAC, admittedly) good reason to possess and the ability to possess the firearm/s without risk to the public, that there is an entitlement to be granted the certificate.
Indeed, why are these things called 'certificate' rather than 'licence'?
My suspicion is that the folk who drafted the Act in 1920 were aware that British subjects have authority under common law/Bill of Rights to possess arms. The 'certificate' therefore is a document certifying that the holder is a
fit person to exercise that right, and not a 'licence' which
gives permission to do so.
Does that make any kind of sense?
The old 'Gun Licence' (1870 Act) did indeed
give permission to carry a gun outside the curtiledge of the owner's dwelling-house. No restriction on purchase or possession resulted, and AFAIK, there were numenrous exemptions for Game-licence holders, vermin-shooters and so on.
Jimbo is more succinct:
We do technically have a right to bear arms but the goverment has trampled all over it , technically yes it's a right but in practice a privilege
but I must say that I have never felt it a priveledge to have FAC or SGC. If it is indeed a priveledge in practice, then the blame for that should probably be shared among any shooters and FLD-employees who behave as if it were.