Broker data, page-31

"Shorters can short/buy back - repeat many times and still report the 'shorts' only - when in fact they may have actually bought more for the day than sold!" yes
ASIC and ASX rely on the trader or broker to do the right thing, they cant verify that the reports are actually correct.

"Also I've reached a conclusion that the aggregated shorts are only those borrowed for shorting and may/or may not have actually have been traded at all!"
No, aggregated shorts are those which have been sold and not bought back yet.

Borrowing shares is a separate step, which must be done before selling, it involves entering a contract with the lender, then those shares are moved from the lenders account to the borrowers.