they're saying we need brief invulnerability AS we're attacking so we don't end up taking damage as we're destroying an enemy, also the timing for the attack reset should be more forgiving, and actually landing a hit that gets the speed boost should also prolong the hitbox of the attack itself and grant more i-frames in the event there's two or more enemies close enough to where that speed boost causes us to get hit as there's not enough time for us to swing again before colliding with the enemy