I think they can detect cheaters once they already win since they can see the pattern of this bastard and just halt their withdrawal. The problem was damage was already done and those codes that claimed by cheaters will never be distributed again. This is the downside of having a cash drop in public to attract new players. The current promotion doesn’t function it’s purpose since it’s very quick to claim which new users doesn’t have any chance to use it.
I become tired claiming this codes since last Christmas Giveaway which many bot twitter account participated on the contest that kill those legit players chance of winning.
Cheaters will always find new ways to abuse the system so it is very hard to get that under control. I don't think these cash drops really gets the attention of new users, it is more a way to reward old users. Personally, I don't get why Twitter is still popular and that a lot of casino really use it. It is full with bots and I really doubt if it is really so effective for marketing.