Point being allowing Pumpkins to grow onto snow blocks and make them. I know an entity must place them. And thickness isn't used, so...
This all reminds me: Anyone make a Enderman making an Iron Golem comic, yet? We have a few for Snow Golems... Would be funny like a sequel. Sees Iron Golem spawn, giving Villagers flowers. Carefully places pumpkin on it, runs. Looks back, Iron Golem pissed.