I've played in 999Dice last week, Deposit 0.1BTC , withdrawed 0.12BTC after few hours of playing and i received my deposit in my web wallet. So i will not say that this site is scam.
You say 999dice is not scam just because you won 0.02btc and you received your withdrawal but you ignore the fact about the huge numbers of scam accusations against them?
But of course it is your own choice wherever you want to put your money, at least this forum has advised you about the reality of 999dice.
Yes,he could able to say such thing because he have been payout by 999dice but same as you said hes not aware on the past negative accusations of the site. He might recieve payout because its not really a big amount and would not tend not to payout and increase their accusations now.