Problem I see with this design is it depends on their stinger sliding freely in your receiver to actuate the strain gauge (and there fore the brakes). I don't see that being reliable in the long term.
They do appear to make the same setup that replaces the tongue of your trailer. But setup appears to have the same flaw.
In both cases you would need a roller setup to allow repeatable movement to actuate the brake controller. Or at least I don't believe depending on a greased receiver is the best idea.
Version 2.5 is a class IV stinger for larger 2 1/2" receiver. Version 2.0 is for smaller 2" receivers. Also it looks like you could have weight
distribution hitch, but it would require welding or bolting on the hardware.