It ain’t just on when the characters are coming out through snapbacks or KO, you can do it during the game but you just got to time it right. That attack does and can hit 2 times so I think that’s why it’s a unblockable cause the AI only registers it as 1 hit when it’s 2 hits. I don’t think it depends on distance but if you’re mid screen and further then it’s best to do it.
Just time it as the character is coming out or when a character super jumps and is coming down. I do this sometimes but I usually do:
[LIST]
[]Fly, HP, Unfly, HP, Land, d.HP, LP.RP xxx HSF (must have Unfly)
[]Fly, HP, ReFly, HP, Unfly, Land, d.HP, LP.RP xxx HSF
[/LIST]
^I think those are unblockables too cause I usually break their guard at the d.HP.