the command "bitcoin-cli getblockstats 0000000000000000000c61ff8f761ce509fc8901d3c22d61fec89637042ea2ba" does not work.

It displays "error: Error parsing JSON:0000000000000000000c61ff8f761ce509fc8901d3c22d61fec89637042ea2ba"

but it should display the block stats like the documentation says.

also bitcoin-cli getblockstats 0 does not work. block number must be at least 1 to work. But blocks start at 0.

tested with 0.20.1 on freebsd, another user on IRC acknowledged the problem.
{
    return RPCHelpMan{"gettxoutsetinfo",
                "\nReturns statistics about the unspent transaction output set.\n"
                "Note this call may take some time if you are not using coinstatsindex.\n",
                {
                    {"hash_type", RPCArg::Type::STR, RPCArg::Default{"hash_serialized_2"}, "Which UTXO set hash should be calculated. Options: 'hash_serialized_2' (the legacy algorithm), 'muhash', 'none'."},
                    {"hash_or_height", RPCArg::Type::NUM, RPCArg::DefaultHint{"the current best block"}, "The block hash or height of the target height (only available with coinstatsindex).", RPCArgOptions{.type_str={"", "string or numeric"}}},
                    {"use_index", RPCArg::Type::BOOL, RPCArg::Default{true}, "Use coinstatsindex, if available."},
                },
                RPCResult{
                    RPCResult::Type::OBJ, "", "",
                    {
                        {RPCResult::Type::NUM, "height", "The block height (index) of the returned statistics"},
                        {RPCResult::Type::STR_HEX, "bestblock", "The hash of the block at which these statistics are calculated"},
                        {RPCResult::Type::NUM, "txouts", "The number of unspent transaction outputs"},
                        {RPCResult::Type::NUM, "bogosize", "Database-independent, meaningless metric indicating the UTXO set size"},
                        {RPCResult::Type::STR_HEX, "hash_serialized_2", true, "The serialized hash (only present if 'hash_serialized_2' hash_type is chosen)"},