Would you call "get", "set", "del" and "rename" a query language? Because they are commonly used commands for Redis.

There are plenty of databases without associated query languages. RocksDB, FoundationDB, and LMDB to name three. "Queries" are generally "list keys in this range" and all of the higher-level metadata you would want to query on (e.g. relations) are encoded in the key. I would absolutely put filesystems in this camp.

"Language" is just an interface. You can SQL a filesystem if you want, and also can build 3rd party indexers that query engines can benefit from.

Exactly! https://osquery.io is one example that

Path syntax with shell globbing is the query language.

Now add find, grep, xargs, sed, awk and put all those together with pipes

Considering things like wildcards and glob matching these don't seem far off from what you'd use in a graph db query language. (E.g. something like neo4j)