I read that whitepaper before I posted but it was not helpful. It states the following:
The Intel IPP software additionally to the libraries provides special wrapper classes for the functions of several Intel IPP domains: signal and image processing, color conversion, cryptography, string processing, data compression, jpeg coding and math and vector math. The wrappers allow Intel IPP users to call Intel IPP functions in C# applications.
This leads me to believe the wrappers should cover every image processing method, but the ippiAbsDiff methods are clearly missing. I believe this is an accidental omission on Intel's part and I think that Intel should add these missing methods to bring the wrapper in line with what is claimed in the whitepaper and elsewhere in the IPP documentation.
In the meantime, that whitepaper does not describe how to add missing signatures to the wrapper. I tried to add theippiAbsDiff_8u_C1R method to the wrapper but I either guessed the method signature wrong or ippiAbsDiff is in fact also missing from the native DLL (can you check this?).