Synthetics DescribeRuntimeVersions command MaxResults maximum is invalid

As per the documentation for Synthetics:DescribeRuntimeVersions, the maximum value for the MaxResults property should be 100. However, the actually implemented maximum MaxValue is 80. This happens both with the AWS JS SDK v3 and the AWS CLI v2:

$ aws synthetics describe-runtime-versions --max-results 81
An error occurred (ValidationException) when calling the DescribeRuntimeVersions operation: Invalid MaxResults
$ aws synthetics describe-runtime-versions --max-results 80 | jq '.RuntimeVersions | length'
30

There is either an issue with the documentation, or its implementation