He doesn't ask for anyone's coins it seems, just API access and an up front fee. He's offering a service which you can either agree to use and pay for (at your own risk of course), or not. People granting him access to their API keys are retarted, not this dude himself. The dude is looking for a side hustle and there apparently are enough retards out there allowing themselves to be used as a walking money jar he taps into at will.
I'm sure that he first buys himself into the market, then use people's coins to follow and have him benefit even more, especially when it concerns smaller coins with lack of liquidity on both sides of the book.
Don't trust anyone with your coins people (physically or through API access), it's not worth it. Trade it yourself or don't trade at all.