Placing carved pumpkin before snow/iron blocks does not spawn golem until nearby blocks are updated

When creating a block pattern for summoning a snow/iron golem, placing the carved pumpkin before the snow/iron blocks does not spawn the golem until nearby blocks are updated.

Reproduce

• Place a carved pumpkin two blocks above the ground
• Build the base for an iron golem/snow golem under it (make sure the base touches the carved pumpkin)
  Notice no iron golem/snow golem has spawned

Expected Result

The snow golem/iron golem would spawn as normal