C'mon master grinch. Probably English is not their native language. Let me make a bold guess from the very first post.
They want to run SQLite on an NFS share and ask
IF fcntl() style locking is provided by TrueNAS.
Unfortunately I cannot answer that question because I have been running NFS long enough to have learned that one does not simply put anything that requires any locking on an NFS share. No mail spools, no databases, just don't. I lost interest and have no idea if NFSv4 provides a proper locking mechanism. Mainly because running concurrent "database" accesses over file sharing protocols is a bad idea to begin with and real database servers exist.
@marnog I would try to avoid putting any effort into a setup like this and research if e.g. MariaDB or PostgreSQL can be used instead of SQLite.