Some mobs suffocate when under a block and a slab in a bamboo raft, but not any other type of boat

How to reproduce:

1. Build the setup shown in the screenshot:
2. 
3. Spawn any of the affected mobs* near the boat and raft so they sit in it

Observed result:
They suffocate in the raft, but not in the boat.

Expected result:
They don't suffocate in the raft.

*Affected mobs:

• Blaze
• Llama
• Snow Golem
• Trader Llama
• Villager
• Wandering Trader
• Witch