This issue is non-reproducible when using valid parameters as documented for the Create Site REST endpoint: https://developers.arcgis.com/rest/enterprise-administration/portal/create-site.htm
解决办法
Create a site from Portal for ArcGIS home instead, which does not allow the creation of S3 configuration stores for HA.
Alternatively, configure high availability by creating a local config store for Portal for ArcGIS deployment, then moving the config store to the AWS file share (or possibly the S3 bucket).