The repl arch guide states:

Snapshot read concern can only be run within a multi-document transaction. See the Read Concern Behavior Within Transactions section for more information

Which according to our public docs and is no longer true as MongoDB v5.0 and a find with a snapshot read concern works in v8.0 test cluster.

Recommend updating the guide to state that find, aggregate, and distinct (for unsharded collections) are supported outside of a transaction