Air pressures change with the temperature of the wheel/tire. If one side is in the shade it might read lower than the side in the sun by a couple lbs. Seems very rare to have tow rims or tires leaking on the same side at the same time and rate. Also makes a difference after running down the highway with heat buildup. I always expect that my pressures could go up as high as 5lbs or more when running on a very hot day at high speeds. So if you set pressures on the high side cold they might exceed the max rating when they are hot.
I have had tires fail (separate) after adding too much pressure cold and heading down the highway on 100+ days. Actually three out of four over about 200 miles. Now I keep them about 5 lbs below the max I want for the tire and load rating and no problems.