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.
{RPCResult::Type::STR_HEX, "muhash", true, "The serialized hash (only present if 'muhash' hash_type is chosen)"},
                        {RPCResult::Type::NUM, "transactions", true, "The number of transactions with unspent outputs (not available when coinstatsindex is used)"},
                        {RPCResult::Type::NUM, "disk_size", true, "The estimated size of the chainstate on disk (not available when coinstatsindex is used)"},
                        {RPCResult::Type::STR_AMOUNT, "total_amount", "The total amount of coins in the UTXO set"},
                        {RPCResult::Type::STR_AMOUNT, "total_unspendable_amount", true, "The total amount of coins permanently excluded from the UTXO set (only available if coinstatsindex is used)"},
                        {RPCResult::Type::OBJ, "block_info", true, "Info on amounts in the block at this block height (only available if coinstatsindex is used)",
                        {
                            {RPCResult::Type::STR_AMOUNT, "prevout_spent", "Total amount of all prevouts spent in this block"},
                            {RPCResult::Type::STR_AMOUNT, "coinbase", "Coinbase subsidy amount of this block"},
                            {RPCResult::Type::STR_AMOUNT, "new_outputs_ex_coinbase", "Total amount of new outputs created by this block"},
                            {RPCResult::Type::STR_AMOUNT, "unspendable", "Total amount of unspendable outputs created in this block"},
                            {RPCResult::Type::OBJ, "unspendables", "Detailed view of the unspendable categories",
                            {
                                {RPCResult::Type::STR_AMOUNT, "genesis_block", "The unspendable amount of the Genesis block subsidy"},
                                {RPCResult::Type::STR_AMOUNT, "bip30", "Transactions overridden by duplicates (no longer possible with BIP30)"},
                                {RPCResult::Type::STR_AMOUNT, "scripts", "Amounts sent to scripts that are unspendable (for example OP_RETURN outputs)"},
                                {RPCResult::Type::STR_AMOUNT, "unclaimed_rewards", "Fee rewards that miners did not claim in their coinbase transaction"},
                            }}
                        }},
                    }},
                RPCExamples{
                    HelpExampleCli("gettxoutsetinfo", "") +
                    HelpExampleCli("gettxoutsetinfo", R"("none")") +
                    HelpExampleCli("gettxoutsetinfo", R"("none" 1000)") +
                    HelpExampleCli("gettxoutsetinfo", R"("none" '"00000000c937983704a73af28acdec37b049d214adbda81d7e2a3dd146f6ed09"')") +
                    HelpExampleCli("-named gettxoutsetinfo", R"(hash_type='muhash' use_index='false')") +
                    HelpExampleRpc("gettxoutsetinfo", "") +
                    HelpExampleRpc("gettxoutsetinfo", R"("none")") +
                    HelpExampleRpc("gettxoutsetinfo", R"("none", 1000)") +
                    HelpExampleRpc("gettxoutsetinfo", R"("none", "00000000c937983704a73af28acdec37b049d214adbda81d7e2a3dd146f6ed09")")