I’ve done it a few times, in a couple of different ways, but not recently.
The only time I hired two escorts who didn’t know each other was a scheduling mistake on my part, on a trip to Las Vegas about a decade ago. It worked out rather well. However, unlike the poster who was afraid the escorts would get it on with each other, I was hoping (after I realized I’d be seeing them both at once) that they’d do something with each other. Instead, each interacted only with me. I did enjoy them both, one at a time and simultaneously.
I’ve also hired couples although, again, not recently. I assume that’s not what you’re asking about.
The third variation is that sometimes, after I’ve been with an escort one or more times, I’ll ask if he likes 3ways and suggest that he pick the third person. Although I’ve had at least one reasonably good experience, I’ve found that escorts aren’t usually very good at figuring out which characteristics turn me on, and they select someone who’s not quite right for my tastes.