because melee hits auto target them, so if u melee twice then quick throw the spear, it almost always hits, and 100-0ing them without prior warning makes it even easier. the throw being in melee range basically makes it an auto targeted hit scan throw
edit: and, like i said, its less than 2 seconds to kill from full hp, doesnt require any weapon switch or previous set-up. its a kill equivalent to the time it takes to melee 3 times with stick
edit2: beartrap kills are easy too, but not as easy. ive killed throwing spear then coming later and meleeing them too, not as easy. easy, but nto as easy, because they get a warning and the whole team is ready for “something” to happen