I summoned a falling_block entity with an end_gateway, and the falling block entity was invisible. Once the falling block landed, the end gateway block was placed. I used these commands:

• 1.13 snapshot: /summon minecraft:falling_block ~ ~5 ~ {BlockState: {Name: "minecraft:end_gateway"}

  ,Time:1}

• 1.12.2: /summon minecraft:falling_block ~ ~5 ~ {Block:"minecraft:end_gateway",Time:1}

This is also the case with minecraft:end_portal. 

The bug:

falling block entities are invisible if they should have the texture of a end gateway or end portal