I had the lead majority of the match if not all(have to look at it again) so the Meta Knight would have to approach. It was working because I was spacing myself to where he couldn't punish it and if he could punish it, my back would be at the ledge, so he wouldn't be able to kill me super early unless he wants to risk his life(Because you can airdodge through tornado and DI the Nair).
It is indeed predictable, but very annoying to deal with which makes it fairly spammable. Majority of characters have a hard time punishing it and was forced to respect it. Sure they can camp at the ledge, but if I have the lead, they would have to approach me eventually. Meta Knight is just one of the few MUs that I do abuse PK Fire much more than other characters. Many other MUs i don't use PK Fire nearly as much besides throwing it out there so the opponent has to respect it.