Therefore a "short" field landing speed should by definition be the same as a normal landing i.e. not below the AFM speed
Most of Tee Emm's flying has been on heavies where book speed is the aim with only minor additives involved.
I suspect that the CASA concern is with the oft-seen GA approach at speeds considerably higher than book speed .. ergo .. the intention is to ensure that the candidate can manage a satisfactory book speed approach and landing.
Other than for specific approvals, civil standards don't address STOL ie there is no defensible reason for approaching below AFM/POH book speed. If one does, and screws the landing up somewhat, then one ought to have a good story in mind for the Inquiry. The only story I can see being valid is something tied up with an emergency or other non-normal high priority situation. (Yes, I know .. we've all done it but it really isn't a routinely good idea).