Back in February, eventshub.com reported on a glitch in Super Smash Bros. Ultimate that caused Sephiroth’s One-Winged Angel mechanic to trigger early in certain situations while facing off against the Pokémon Trainer as an opponent. If the Pokémon Trainer performs the Pokémon Change special while Sephiroth is at 80% damage or more, then the One-Winged Angel buff will activate regardless of Sephiroth’s lead.
Not only has the glitch not been addressed in patch 11.0.0, but the effect has carried over to Pyra & Mythra. If either of these Xenoblade Chronicles 2 reps use their down special while Sephiroth has accrued 80% damage or more, then he’ll be awarded his wing earlier than typically intended.
Sephiroth’s One-Winged Angel functions similarly to a comeback mechanic in a fighting game. If Sephiroth is fighting from behind, then his wing will sprout before reaching 80% damage.
However, if Sephiroth has taken a stock lead over the opponent, then Sephiroth might have to take a little more damage before getting access to his insane buffs. At equal stocks, the damage threshold is set to 80%.
When the Pokémon Trainer switches between Squirtle, Ivysaur or Charizard, the Pokémon Trainer briefly stops counting as a character. This causes Sephiroth’s One-Winged Angel algorithm to go a bit haywire.
Since Pyra & Mythra’s down special also swaps characters between the two, we can conclude that they also briefly stop counting as a character during the swap effect.[source eventhubs.com]