I can't say whether this is a scam or not, but what is certain is that I am sure the risk is very big to invest in these altcoin, so my advice is not to invest all your money in these altcoin, because the possibility of you losing your money is very high, then you also shouldn't be greedy, so if you have made a profit from these altcoin, then I suggest you to take the profit and don't hold it for the long term, because the risk is very high.