According to the IEEE802.3at specification, a type 2 PSE that does not provide 2-event physical layer classification must provide data link layer (DLL) classification. A PSE using TPS23851 for ethernet power falls into the latter category as it does not support 2 event physical classification.
The IEEE spec has more information in section 33.6 about DLL classification, but your software engineers will have to work out the implementation details for your ethernet PHY.