The bug

Summoning a villager with an empty Offers tag correctly spawn a villager which cannot be traded with. However, when reopening the world the villager has trades.

How to reproduce

1. /summon minecraft:villager ~ ~2 ~ {CustomNameVisible:1b,PersistenceRequired:1b,Health:20000f,CustomName:"{\"text\":\"John\",\"bold\":\"true\",\"color\":\"green\"}",VillagerData:{level:1,profession:"minecraft:leatherworker",type:"minecraft:snow"},NoAI:1b,Offers:{}}
   

2. Right click the villager
   → It cannot be traded with
3. Reopen the world
4. Right click the villager
   → It has trades