After Teemo, Strategist's errata, does he ever trigger when played from Hidden outside of a Showdown?

Does Teemo, Strategist's errata completely prevent him from triggering when played from Hidden outside of a Showdown? The errata was meant to stop him from triggering twice at once when played from Hidden as a defender, but playing him as a Reaction to a moving effect like an enemy's Eye of the Herald happens at a totally different timing, outside of any Showdown.