Minecraft wiki entry for NBT_format, associated text: They check only for the presence of the provided tags in the target entity/block/storage. This means that the entity/block/storage can have additional tags and still match. This is true even for lists: the order and number of elements in an list a list is not considered, and as long as every requested element is in the list, it matches even if there are additional elements. For example, an entity with data {Pos:[1d,2d,3d],Tags:["a","b"]} can be targeted by @e[nbt={Pos:[3d,2d,1d]}] or even just @e[nbt={Pos:[2d]}] even though the former represents a totally different position and the latter is not a valid position at all. Note that @e[nbt={Tags:[]}] can't match it, because an empty list can only match empty list.