Excessive Ass Brushing

I've noticed that during the massage portion of my visits, several providers will trace their fingers around my asshole for what feels like ten minutes. What is that?

I'm a FS regular so it's not like they're testing the waters, yet it almost does feel like a test or a signal for something. Are they waiting for me to do something specific? I'll lift my pelvis to give them access to the rest, and sometimes they'll briefly venture further to caress my balls from behind (love that!), but before long, they're back to brushing my ass crack.

That alone doesn't turn me on so I'm usually still flaccid at the flip which makes for an awkward start of the main attraction.

Is there some way to tell them to move on without giving the impression I don't want more?

This is multiple places so it's not like an isolated incident...