Well only people with poor thinking and people that don't have enough knowledge in cryptocurrency will be victimized by this. When someone ask for your private key or anything that can be use to access your Bitcoin wallet, that is enough reason not to transact with those people they will surely do nothing good. And also why would anyone will send you 1 Bitcoin and give him half of it after you receive it, if he can keep that 1 Bitcoin by himself? lol. No one with straight mind will give 1 Bitcoin for free without having anything valuable in exchange. This is a lesson that should everyone know especially those people that are just starting investing in cryptocurrency, never transact with other people without an escrow service because Bitcoin/cryptocurrency transactions are irreversible.
But there's still a lot of people who fall for this trap and its good that the OP has given us a warning about the said modus operandi. Lessons here is not to trust anyone, specially people you really don't know and just met online.
They are taking advantage of those people in the crypto that will jump because of the huge offer of 1
BTC, lest they know that they are going to be another statistics from those scammers out there.
So just be really careful, don't be greedy and used our common sense and not be a victim here. I myself have been scam in the beginning of my career in a HYIP, but since then I said that I will not be victimized again.