all jumping attacks are overheads, but it doesn't necessarily make them "instant overheads". instant overheads are usually applicable to jumping attacks which have very fast startup with low hitboxes. a fairly common example is leona's neutral j.D into v-slasher. because of the downward angle of the attack, if you j.D immediately after a neutral jump, the active frames hit low enough even on a crouching opponent ,hence, instant since it's pretty hard to react to.
i didn't mean to add strategy/gameplay to the thread, but i figured i'd throw it in there since i looked that part over. also, i don't really want to mess around with the 2k2 wiki since i don't really play that game anymore. feel free to use this information, however, and delete this post at your discretion.