OData Connector does not perform POST $batch requests -in all selectable versions- and is therefore NOT OData compliant.
Despite the company Devart would have us believed.
Please kindly refer to this link and look at the OData Minimal Conformance Level, OData Intermediate Conformance Level, OData Advanced Conformance Level sections. Batch requests are related to the extended functionality and are listed in the OData Advanced Conformance Level section (11. MUST support batch requests (section11.7 and all subsections)). Skyvia Connect supports most features from the extended functionality, however, batch requests are no supported at the moment. We will definitely inform you if any news regarding this functionality is available.