APO is a great use case for machine learning once enough data has been accumulated, that could also automate testing and should provide results in a much smaller timeframe. At least that's what I would try with APO, because manual tuning after every patch and for each new game (or even application, not like Photoshop for instance has great multithreading, could probably also benefit from APO) release would otherwise only be feasible if the optimizations could somehow be handed over to the community.
Well, those are here to stay, what with AMD adding "c" cores to their CPUs in the future. Oh, they sure like to tell how much better their c-cores are going to be to Intel's e-cores because they're basically the same and thus have the same IPC, just more tightly packed and clocked lower, but one just needs to look at the 7900X(3D) and 7950X(3D) and its myriad scheduling problems to give lie to that statement. There are games where a 7700X beats the 7900X and 7950X due to coordination issues between separate CCDs that are identical, and the 7800X3D is consistently as fast or in some cases even faster than the 7950X3D - and that is with the artificially lower clock speeds of the 7800X3D.
Having cores that clock lower is going to be an issue for scheduling, whether or not they have the same IPC, and between Intel's Thread Director and AMD's core parking on the 7900/7950X3D, the conclusion is pretty obvious. The c-cores are not going to have the same performance as the regular cores, and therefore AMD's going to run into scheduling issues, unless they just turn off the c-cores in gaming like they do with the 79X0X3Ds - which also not always works properly. Proof is in Steve's benchmarks.
With the way APO seems to work according to Hardware Unboxed's video, i.e. making sure one e-core per cluster has access to the full cluster L2 cache by turning the other three off and directing threads to make better use of the CPU, it sort of makes sense that the only supported CPUs so far are the 14900K and 14700K. APO might not work properly or produce no real performance uplift on a 14600K with only two e-core clusters. The 13700K also has only two of them, so for 13th gen that probably would just leave the 13900K.
Not unlocking APO for the 13900K is a pretty lame move though, if understandable from a marketing point of view (assuming APO becomes more than a tech demo). There's no reason it would not work just as well on a 13900K, seeing how the 14900Ks are just 13900Ks that won the silicon lottery. I mean, like literally.