Virtual Card was created for ONLINE transactions.That makes no sense. Why would scan work but not tap?
Tap to pay was for retail outlets, where you would tap your physical card on the POS device to process the payment.
Since you cannot Tap your virtual card, as you can't actual hold it. Makes sense to me that you cannot select it to TAP via FNB pay.
Snapscan/ zapper/ masterpass, was always a digital/ online method of payment, hence you can use the virtual card.
Not quite difficult to understand, but each to their own