Finally went down and found out from the agents there.
1st and 2nd buyers are the same. 23% nett. +/- 1% for those HDB address or ex-far east/fraser owners.
BUT there is a loophole. Not sure if it is legal though. 7% ABSD can be "transferred" to bank loan. Don't ask me how they do it. Go down and you will find out. I didn't buy so not sure if it really works but sounds workable to me.
For example, 1M property.
First buyer - Nett purchase price 770k. Loan 616k loan(assuming 80%)
Second buyer - 770k. 54k ABSD. 670k loan
So there is no extra discount for 2nd buyer.