We use the mongodb shard cluster, event collections use unsharded. But now the event collections in multiple nodes, why the number of nodes, not only in the primary shard

mongos:

{ "_id" : "event", "primary" : "node02", "partitioned" : false }

node01:PRIMARY> show dbs;
account 0.000GB
admin 0.000GB
alliance 0.000GB
battle 0.001GB
cache 0.000GB
cheating 0.000GB
chest 0.000GB
common 0.001GB
event 0.000GB
guide 0.000GB
local 0.024GB
mail 0.000GB
message 0.000GB
mission 0.000GB
pve 0.000GB
pvp 0.000GB
reward 0.000GB
statistic 0.000GB
store 0.000GB
node01:PRIMARY> show tables;
iap_display
platinum_shop
special_offer
special_offer_count
special_offer_refresh_count
store_refresh_count
supply_drop

node02:PRIMARY> show dbs;
account 0.000GB
admin 0.000GB
alliance 0.001GB
battle 0.001GB
cache 0.000GB
cheating 0.000GB
chest 0.000GB
common 0.001GB
event 0.000GB
fang 0.000GB
guide 0.000GB
local 0.016GB
log 0.001GB
mail 0.000GB
message 0.000GB
mission 0.000GB
payment 0.000GB
pve 0.001GB
pvp 0.001GB
reward 0.000GB
statistic 0.000GB
store 0.001GB
test_demo 0.000GB
node02:PRIMARY> show tables
platinum_shop
special_offer
special_offer_refresh_count
store_refresh_count
supply_drop