I was in AZ a few days ago dumping/recycling used oil and thought of this thread but had to think about which application number it was. Went to the ST2 and sure enough, orange-ish silicone adbv. Thought I'd check out some other STP blue applications, those still nitrile.
I tried to think why topic application with silicone and then thought bet primary use is Ford applications. As I skimmed post didn't see xref to 820S. Anyway, that is true. Mid to late 2000s I remember when family member owned 4.6L Explorer, early on in ownership quick lube used jobber filter with nitrile adbv, had a start up rattle. Switched back to 820S with silicone, rattle gone. That was well before the 820S anecdotes with issues posted, and the ones I cut open were ok. OLM light on that vehicle set to go off at 5k miles, so never went much beyond that. Based on that experience, my "speculation" at least 'some' Ford applications sensitive to drain back and thus the use of silicone adbv in ST2. In 4.6L, filter orientation, dome end ~45° down from horizontal.
The topic filter is the new AZ STP blue with China coo.