So either my memory is bad, or on all of my recent (tubeless wheelsets), about 5 of them, there's a relatively large drop in spoke tension when you mount a tire and air it up, way bigger than anything I can remember in the years before (didn't build any wheels for about 5 years or so in between). I'm thinking tubeless wheels+tires where the tire fits so tight now that there's very little stretching and it causes the tube to push back on the rim some, squeezing it a bit. Maybe seems a little crazy, but when I get it to acceptable tension without a tire and tube (tube for setting the tubeless strip), then install, tension drops way off to below acceptable.