21 days to verify banking details

This isn't a complaint or a compliment, rather a question that no one at SARS can answer. If my bank can verify me at home affairs in 24-48 hours, why does it take SARS 21 working days to verify my banking details? From what I've read, in some cases even longer. Surely with all the tech available to SARS, and the banks for that matter, it cannot take that long. Can anyone answer this question logically or, like in most state entities, does logic not apply?