Yasuo Shield allows him to execute even when he's been attacked

The damage mitigated by Yasuo's shield acts differently than all other shields in the game, in that it regards him as not being hit at all, even when crowd controlled. Things like zilean's slow, a slow from randuins omen, or exhaust all apply a slow without dealing health damage, yet will still get the kill from a tower. However a snare from Nautilus auto attack isn't enough to get the kill instead of an execute.