Note that is not an expected measure of accuracy or their standard. That's the unit increment that the appliances show the readouts in.
Even with the Swifts and Perdii It is not uncommon to see variations: 2 Swifts on the same tank, two Perdii on opposing wrists... Usually within a few psi of each other, but there are times when I've seen bigger splits, though usually less than 26 psi. They almost always come back to within a couple PSI momentarily when I've observed bigger splits.
PWII. Not worth fussing over.