See TODO in jstests/noPassthrough/query/lookup/lookup_sharded_no_join_opt.js. Removing those lines causes the test to eventually fail with:

"error" : "Error: Error: command failed:

{\n\t\"ok\" : 0,\n\t\"msg\" : \"giving up after validating admin: catalog list operations consistency check failed new Error(\\\"socket exception [CONNECT_ERROR] server [Connection handshake failed. Is your mongod/mongos 3.4 or older? :: caused by :: network error while attempting to run command 'hello' on host 'localhost:20043'  :: caused by :: dbclient error communicating with server localhost:20043 :: caused by :: futurize :: caused by :: Connection refused]\\\")\"\n}

"

Probably a bad interaction with a sharding consistency check that we need to fix.