This thread is often referenced
https://www.ft86club.com/forums/showthread.php?t=91820
Like you said, concern is not about oil breakdown. Rather, it's about proper pressure, which is an indicator of pumping effectiveness and oil flow.
Pressure curves and data (both as a function of time over a lap and map versus temperature) are out there and especially concentrated in this forum. [ Google: oil pressure site:ft86club.com ]
In the end, it's whatever condition you decide you're comfortable running the engine. Usually the breakover for people's comfort level hits around 260F. In practice, it's not hard at all to reach those kinds of oil temperatures on the track. It's usually not a concern for street driven cars, but it's still easy to raise temperatures to that level on a spirited high-rev drive on a curvy road
Subaru thinks that 73psi (500 kPa) at 6k RPM is nominal for 176F (80C) oil temp; that works out to about 13psi per 1k RPM