I am aware of their lottery and also looked at the data on Twitter, but I know that this is just smoke and mirrors and any results are rigged by manually indicating to the User the % chance of winning.
Your previous assumptions were already proven wrong, so it is not possible to rig the lottery in the way you think it can. You can’t arbitrarily assign a specific user's tickets a higher weight. Each individual ticket has the exact same chance, and nobody, including FreeBitco.in, can know which user is going to win until after a designated Bitcoin block in the future, from when the ticket file is published, has been mined. The winning ticket number will correspond to a user ID that is already determined in the ticket list, they cannot change who this ticket is assigned to after the fact.
Yes the lotteries that are based on the blockchain, they are hard to be rigged. The only way to cheat in these lotteries is that the site doesn't tell publicly which bitcoin block they will take into account and if they hide this, you would
straight away know that it is a scam. So in other words, you can't change the results in such lotteries.
However, I understand that from where he is telling his concern, as most of the offline lotteries are rigged. Secondly, freebitco isn't the trusted site anymore and this adds weight to his concern.