JSON_UNQUOTE re-encodes each byte of a VARBINARY document as latin1; JSON_VALUE does not

Reproduced on 10.11.19 (debug build):

CREATE TABLE t (b VARBINARY(20));

INSERT INTO t VALUES ('"ö"');            -- the bytes 22 C3 B6 22

SELECT HEX(JSON_UNQUOTE(b)), HEX(JSON_VALUE(b, '$')) FROM t;

-- C383C2B6   C3B6

JSON_UNQUOTE turns the single character ö (C3 B6) into ö (C3 83 C2 B6): every byte of the binary document is re-encoded as if it were latin1. JSON_VALUE on the same value returns the correct bytes. Expected: both return C3B6.