What I expected to happen was:
When creating a vault block with a different loot table, it would keep that NBT data when placed

What actually happened was:
The vault block seems to have lost it's loot table NBT after being placed

Steps to Reproduce:
1. Give yourself, set, or modify an existing vault block with a custom loot table
2. When placed the block will loose its loot table value (Reverting to the default trial chamber loot)

See before and after placing images below (attempting to give the vault the "minecraft:chests/pillager_outpost" table)