The bug

Doing a /loot give @s ... for a player in Survival or Adventure mode while the player inventory is full causes the items to be deleted, rather than spawned as item entities, contrary to the behavior exhibited by the /give command when the player inventory is full.

Reproduction steps

1. Fill your complete inventory

   /give @s minecraft:wooden_sword 36
   

2. Switch to Survival mode
3. Use /loot give

   /loot give @s loot minecraft:blocks/acacia_button
   

   The command feedback says "Dropped 0 items" and you did not get any item, neither was the item entity dropped