I think I found the root cause. Delta for CompositeProviders is supported only under specific conditions. This is a restriction on the SAP side, preventing egress.
In delta mode, the DTP supports CompositeProviders (object type HCPR) as sources if they are made up entirely of InfoCubes or of DataStore objects (advanced) that are modeled like standard InfoCubes or standard DataStore objects (classic). The target of the DTP must be a DataStore object (advanced). A combination of InfoCubes and DataStore objects (advanced) as PartProviders of a CompositeProvider is not supported for DTPs in delta mode.
I found a blog detailing workarounds for various Composite Provider limitations. I am unsure whether item number 2 applies to this or not.
First of all, thank you very much for looking into it and reaching out internally.
Unfortunatelly, we can't isolate the delta on the SAP side. We still need a way to automatically trigger the delta load, as loading daily this amount of data in full, is not an acceptable scenario.
Looking forward to new ideas from your side, on how we could achieve this.
I have not received a reply yet, so I bumped/pinged/poked my internal thread.
Please do not raise your hopes too high. By my thinking, if SAP does not offer any delta options, then I do not think Data Factory will be able to provide one either.
That is why I was what other entry points there are for retrieving your data.
The reply I received pointed to the same doc you did. If I understand correctly. The issue is that after creating Open Hub Destination (OHD) as Database Table and then when you attempt to create the Data Transfer Protocol (DTP), the desired Extraction Modes are unavailable. (My apologies if this seems obvious, but I do not have an environment to go look for myself.)