For me, as a police officer, "duty grade" means any optic or accessory that I feel has met the standard to possibly take or save someone's life while in use on my patrol rifle. I will try out and vet just about any product as long as it works, it can find a place on my rifle. That being said, I'm not necessarily going to throw a Truglo red dot on it, as I've had some on plinkers that worked fine, and just for giggles threw one on loaner rifle and ran a three-day SWAT training with it. Needless to say, it was not sturdy enough for work, and I would not trust it as a tool to employ lethal force.
The converse of that though, is that apparently the Nairobi Spec-Ops guy was using a SIG Romeo red dot on his kit, and he's definitely more badass than I am. I would hazard a guess that he or his unit had tested that optic and he felt comfortable with it. I'll use knock-off handstops, rail covers and light mounts as long as they hold up, I'm not ashamed, I'm frugal. Heck, the light mount I've used for the last 10 years has been a shotgun barrel/tube clamp...it's held up just fine and placed the light closer to the bore than any other mount.
The converse of that though, is that apparently the Nairobi Spec-Ops guy was using a SIG Romeo red dot on his kit, and he's definitely more badass than I am. I would hazard a guess that he or his unit had tested that optic and he felt comfortable with it. I'll use knock-off handstops, rail covers and light mounts as long as they hold up, I'm not ashamed, I'm frugal. Heck, the light mount I've used for the last 10 years has been a shotgun barrel/tube clamp...it's held up just fine and placed the light closer to the bore than any other mount.