That is too low for a low oil pressure warning. I thought the manual said 10 or 12 psi was the switch limit. Maybe the switch gets "loose" with age, like a stretched balloon. A new one might be higher.
Another reason to not trust idiot light switches, which is basically what this is. And another reason to put in a real gauge.
I have checked my gauge against another and they match but that could mean they are both off of course!!Perhaps.... your nice little pressure pump calibration is off. Do you have another way to measure pressure, for example a transducer connected to your DMM that can be Teed into the hose.
It would be good to know if your pump reading is off, so that your cooling system tests are accurate as well.
Rick
No. I have no need of such a thing.You planning to order a new switch?
You could test it...