I have noticed when looking at PY options (for cash) on the mobile app I am presented with what appears to be a full PY itinerary including PY on the partner segment.
Some options say mixed and some dont, therefore I assume if it doesn't say mixed, it is 100% PY. Also when drilling into the itin details it clearly states Premium Economy on all segments unlike when drilling into the Mixed labelled options, it clearly states 'you will be seated in economy' on the partner segment.
Based on my observations (within the mobile app) AC does legitimately offer full PY options including partner segments.
However when searching the same details on the website, it clearly states Mixed for every option presented including the itins that appeared full PY in the mobile app.
So I don't know which is accurate.
Edit: I have noticed this for some time now, so shouldn't be related to current PY fare issue i see is happening.