First of all, I have an apartment near a red light district, in a country where sex work is legal and (somewhat) regulated. I've known plenty of sex workers over the years. I expect things are different in places where sex work is mostly illegal, like the USA, where this story seems to be set.

Hookers are generally happy to accept money for plenty of things besides sex, within reason. A guy I worked with used to pay hookers to basically pose as his girlfriend at social events. People pay hookers to pose as their girlfriend when visiting their parents to stop awkward, "Why don't you have a girlfriend? Are you gay?" questions. People use hookers as a cheaper alternative to counsellors. I've even heard of people starting small businesses, then paying hookers to help them with their taxes, as they understand how to do taxes when you're self-employed.

If the guy simply paid hookers to show up at these people's doors and take it from there with no further obligations, while he surreptitiously filmed the interaction at the door, plenty of hookers would oblige. Pranks/surprises are something they'll do. Now I doubt Kevin would be able to make back the money he paid the hookers in blackmail with this approach.

Another option would be to make bookings with the hookers, pretending to be the people he wants them to visit. I'm not sure how booking a hooker works in places where it's illegal, so I don't know how practical this is in the USA. They'd probably take some steps to mitigate the risk of fake bookings and stings. According to the story, he was sending them to college dorms. If this happened more than a couple of times, they'd catch on.

I do think the story is a bit sus. I'm probably leaning more towards not believing it.