Can a provider or indeed hobbyist be arrested for getting a hand job at an AMP? The reason I ask is there seem to be a few places that have an established reputation if being massage and HE only and they tend to stay open for long. Does uncle Leo only frown on FS establishments?
Each state words their statutes a bit differently, but the crux of all of them is physical contact with any genital region (other than for a legitimate medical reason) is sex for money and therefore verbotten.
That said, I also know of at least one "jack shack" that has been open for years; and the scuttlebut is that the local LE is cool with that and lets them continue as long as FS is not offered.
What the law says and what is actually allowed are two different things in many areas.
It's illegal everywhere in the US except Nevada brothels.
A few things could be going on with the places you are referring to. Police budgets are finite, they have to prioritize what crimes they go after. The parlor staff might be good at spotting cops, and provide strictly legal services to anyone who they suspect as LE. There could be bribery going on. The reputation for providing handjobs might be entirely falsified. They might throw their staff under the bus claiming they were a rogue employee whenever they are caught. It's possible several of these are going on at once.
Up to you if you want to take the risk of being there the day the equation changes and cops come pouring in.