Hi @james-mke ,
You are seeing the right documentation. There is no OOTB way to detect the duplicate images when you upload through the asset API. The configured OOTB functionality works when you upload it via browser UI or through AEM desktop.
For Asset API, in this documentation http://experience-aem.blogspot.com/2021/03/aem-cloud-service-assets-server-side-check-for-duplicate-file-names.html you will have to write the filter which is this point
3) Add a filter apps.experienceaem.assets.core.filters.DuplicateAssetNameCheck executing for .initiateUpload.json and .createasset.html requests to check for duplicate file names across the repo
This filter will be called every time the request happens to upload asset using the asset API. See the
"sling.filter.pattern=((.*.initiateUpload.json)|(.*.createasset.html))",
this defines when this filter will be called. include this java class in your code and verify. You can modify the logic as per your requirement - to throw error or to upload and just log a message or something else.