Just my opinion, speaking as a guy who's paid a few other places to mill slides, bought commercial milled slides, and as a machinist milling a bunch of my own stuff. Also speaking as a mechanical engineer who works hands-on (not the desk-job nerd kind) with a lot of tolerances and dimensional constraint systems.
I don't know Battlewerx and have never done business with them. However, when I see too many different constraints in a locating system like what you've described (we've got the milled walls of the slide, locating studs, and screw hole bosses, that's 3 different systems), it appears to me that either the company selling it doesn't understand tolerance stackups, or they're selling to people who don't understand it.
Pick one locating system. You don't need 3, even with 2 systems (the typical setup of bosses in a tightly milled pocket) only one of them is actually doing anything. You can locate the optic with the bosses, with loose slide pocket. That's fine, but IME not as good. Or, with an RMR (not most other optics) you can have the pocket milled for a very snug fit to the optic, and that's all you need; any additional bosses or studs have no benefit.
Also, the screw hole bosses means the optic has to be secured with smaller screws than normal. There's no room for the bosses otherwise. I see that as a negative.
So personally, just based on what you've described I would choose someone else. The best work I've had for an RMR slide milling was from Mark Housel at L&M Machining (or something like that). I don't know if he's still in business, that was over 10 years ago, but if he is, I'd trust him to do a quality job.
