This bug report is derived from inspecting the syntax diagram. There is no path to returning-clause without going through WHERE expr.

This might be a documentation-only bug, since the diagrams seem to be manually built and I don't have a copy of sqlite that is both new enough to support RETURNING and was compiled with SQLITE_ENABLE_UPDATE_DELETE_LIMIT.

Test code if relevant:

DROP TABLE IF EXISTS dummy;
CREATE TABLE dummy (x INT);
INSERT INTO dummy VALUES (1), (2), (3);
UPDATE dummy SET x=-x WHERE 1 RETURNING x;
UPDATE dummy SET x=-x RETURNING x LIMIT 1;
SELECT * FROM dummy;

If you get a syntax error on the first RETURNING, your sqlite is too old.

If you get a syntax error on the LIMIT, your sqlite was compiled without SQLITE_ENABLE_UPDATE_DELETE_LIMIT.

If you get a syntax error on the second RETURNING, this bug affects code too.

If you get no syntax errors, then it is a documentation-only bug.

The syntax diagram for DELETE ... RETURNING ... LIMIT is not affected.

(mandatory note that WHERE should always be mandatory because we are all dummies)