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.
"action", RPCArg::Type::STR, RPCArg::Optional::NO, "The action to execute\n"
        "\"start\" for starting a scan\n"
        "\"abort\" for aborting the current scan (returns true when abort was successful)\n"
        "\"status\" for progress report (in %) of the current scan"
};
static const auto scan_objects_arg_desc = RPCArg{
    "scanobjects", RPCArg::Type::ARR, RPCArg::Optional::OMITTED, "Array of scan objects. Required for \"start\" action\n"
        "Every scan object is either a string descriptor or an object:",
    {
        {"descriptor", RPCArg::Type::STR, RPCArg::Optional::OMITTED, "An output descriptor"},
        {"", RPCArg::Type::OBJ, RPCArg::Optional::OMITTED, "An object with output descriptor and metadata",
            {
                {"desc", RPCArg::Type::STR, RPCArg::Optional::NO, "An output descriptor"},
                {"range", RPCArg::Type::RANGE, RPCArg::Default{1000}, "The range of HD chain indexes to explore (either end or [begin,end])"},
            }},
    },
    RPCArgOptions{.oneline_description="[scanobjects,...]"},
};
static const auto scan_result_abort = RPCResult{
    "when action=='abort'", RPCResult::Type::BOOL, "success",
    "True if scan will be aborted (not necessarily before this RPC returns), or false if there is no scan to abort"
};
static const auto scan_result_status_none = RPCResult{
    "when action=='status' and no scan is in progress - possibly already completed", RPCResult::Type::NONE, "", ""
};
static const auto scan_result_status_some = RPCResult{
    "when action=='status' and a scan is currently in progress", RPCResult::Type::OBJ, "", "",
    {{RPCResult::Type::NUM, "progress", "Approximate percent complete"},}
};
static RPCHelpMan scantxoutset()