Shortly after I posted that reply, I got similar correspondence to the one you posted, asking for more details on the home office and medical expenses, from square meterage (this was already on the floor plan I sent) to the photos and a whole lot more.
I sent all of that in last night, and then this morning, woke up to a new "Revision submitted by SARS" for the ITR12.
My new ITA34 now indicates R5926 (the previous one was -R10k). All of my home expenses have been removed. Statement of account indicates -R4k.
I'm on the phone with the contact center now, number 500 in the queue