Matt DiStefano shares his screen and rotates a gray 3D model of a California neighborhood. He zooms in on one house and overlays a heat map. Red contours run along the sides and back, where trees stand close to the home. Blue sits near the pool. Then he starts deleting trees. Removing one takes more than $1,100 a year off the home’s premium. Another, he says, “doesn’t contribute as much.” “This one’s the one that matters,” DiStefano says of the first tree. He is Stand’s 29-year-old chief science...