That´s right, you can still kill them but you won´t get any more cards from the same boss
in these 6 hours. That´s why the twinks change positions so that they can kill another boss and get the other card.
Then you can put the twink back in its old position.
That doesn´t change anything about camping except that now more transport runes are needed
for twinks who don´t have VIP.
Why the buff is canceled by killing another boss, you have to ask the people who programmed the buff.