This one is interesting. Would love to see how internals are.
In regard to HLP oxidation, the virgin oxidation value for PCMO is 23-25. What you have to look at is the change from virgin/used. HPL wear control is very good. TBN is as strong as I've ever seen in any oil. Just thinking out loud, I wonder when HPL starts to show signs of oxidation via oxidation value or KV, that the high solvency bases that are claimed to be used, and high detergents, keep any deposits/varnish/sludge from forming. In other words, maybe HPL is so capable of holding contaminants in suspension due to high detergents that it will oxidize a bit faster, but also keep the engine much cleaner.
Just a thought.