Is the oil pressure sending unit upstream or downstream of the filter?
If the sensor is upstream of the filter, a restrictive filter would LOWER the pressure. But not by a lot, because the oil filter bypass should open to allow flow.
Some folks plug the oil filter bypass. I don't.
On Chevy gen 1 small blocks oil flows from pump, through rearmost main bearing, through filter, then up to rear of main gallery right next to the pressure sender, and through rest of the system.
if flow is restricted through filter (from plugged media—regardless if it’s dirty media or media that restricts flow), the filter bypasses. In bypass state the main gallery receives a stronger flow because the oil is no longer having to flow through media (and all properly functioning filters slow the flow down somewhat), and will show higher than normal pressure. That’s why on cold start we see a higher pressure reading than hot engine oil pressure.
Now, I know that you know all of the above and are just testing me.....
With the Purolator Pure One it pegged the oil pressure gauge on start up (I’ve never seen that even in 20 below weather with the truck left outside) This suggests that almost ALL the oil flow was being bypassed up to the main gallery where the oil pressure sender is located.