Q. I was told that there is a problem for Noachides to eat regular treif meat, because it is stunned/killed and then cut up while it’s still moving (it is ever min hachai because it is still m’farchses)

A. Shulchan Aruch (Y. D. 27: 1) rules that it is prohibited to eat from parts cut from an animal that has undergone shechita and it is still fibrillating, until the animal dies. Once the animal died, Shach (ibid. 2) and Taz (ibid 1) quoting Tur, maintain it is permitted even to feed its meat to a Gentile. However, if there was no proper shechita and parts were cut from the animal while it was still alive and twitching, even after the animal dies the parts remain prohibited.
In reality, in most modern slaughterhouses after bovines are killed by using the common captive bolt pistol or similar, their throat is slit to let them bleed. Then the head is first removed at least partially before the animal is skinned. By the time the body is cut open to remove the entrails and begin dismembering, it is very likely already dead. Although some animal rights reports will have you believe that animals are skinned and dismembered while still alive, it is unlikely and the clear roiv or majority of cases is otherwise.
The fact that occasionally some muscle spasm occur in a partially dismembered bovine, is not an indication that the animal is still alive. They reflect what the Talmud (Ohalos 1: 6) refers to as the contractions of the separated tail of a lizard.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a