Health of all the shards from mongos - showing incorrect

I have 4 shard nodes, I have stopped 1 shard service to see how mongos will show the state of that down service. My goal is to find the complete down shard from mongos:
The commands I checked with:
It show all the shards are healthy, i.e. false, i have stopped shard service.
db.serverStatus() --show cluster uptime, but I want any error here.

When I am doing show dbs, it shows error message, that is expected.

My question is:
why sh.status() is not aware of any down shard, no node for shard 2 is working.
How to find any down shard from mongos?