I thought you were talkin' 'bout deliberately waiting at a fixed/probable spawn areas, camping patiently, and murdering 'em as soon as they appear. I don't consider the examples you listed as spawn killing; or at least, not the bad kind. In those situations, luck is the reason it's happening, not malicious playstyle. Someone's gotta die, so it might as well be who's the quicker draw.
Differences in gaming communities' definitions: always sparking pointless discussions. I'm a veteran of Red Dead's competitive team modes, and the most infamous known spawn killing method is a certain map where control of the cannon means you can spawn kill roughly two people each time ya bloody fire across the map, since there are only two spawn locations for this particular map in this particular team mode. Guarantees victory for whoever grabs the cannon first. Poor map design, to say the least... Another map has a very similar problem, though only half as bad. At least they give you a sniper to take the bastard off the cannon if they miss their shot.
Point being, Red Dead'ers refer to spawn killing as using predictable or even guaranteed fixed spawns and the lack of spawn protection/invincibility to gain a ridiculous game-breaking advantage. Anyone who participates in such skill-lacking debauchery is too bloody srs about the game, or a troll.