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.
ret.pushKV("txcount", (int64_t)pindex->nChainTx);
    ret.pushKV("window_final_block_hash", pindex->GetBlockHash().GetHex());
    ret.pushKV("window_final_block_height", pindex->nHeight);
    ret.pushKV("window_block_count", blockcount);
    if (blockcount > 0) {
        ret.pushKV("window_tx_count", nTxDiff);
        ret.pushKV("window_interval", nTimeDiff);
        if (nTimeDiff > 0) {
            ret.pushKV("txrate", ((double)nTxDiff) / nTimeDiff);
        }
    }
    return ret;
},
    };
}
template<typename T>
static T CalculateTruncatedMedian(std::vector<T>& scores)
{
    size_t size = scores.size();
    if (size == 0) {
        return 0;
    }
    std::sort(scores.begin(), scores.end());
    if (size % 2 == 0) {
        return (scores[size / 2 - 1] + scores[size / 2]) / 2;
    } else {
        return scores[size / 2];
    }
}
void CalculatePercentilesByWeight(CAmount result[NUM_GETBLOCKSTATS_PERCENTILES], std::vector<std::pair<CAmount, int64_t>>& scores, int64_t total_weight)