In the "General limitations" sections of "Limitations" page for mongosync public documentation, its written "Queryable Execution is not supported."

"Queryable Execution" should be "Queryable Encryption" as that is the page its linked to.

https://www.mongodb.com/docs/cluster-to-cluster-sync/current/reference/limitations/#:~:text=Queryable%20Execution%20is%20not%20supported.