It's in the middle of a large, disturbed area with big commercial buildings, roads, and parking lots, only some of which are data centers. This type of disturbance tends to get hot in the sun. But the larger question is how they are attributing the temperature at the end of the cul de sac to the data center when the somewhat more obvious reason for a hot spot there is that nothing shades it. That is, the measured cooler streets are shaded by the houses, but the edges of the neighborhood are shaded by nothing.

Anyway the main problem with this paper is it does not have an explanation for why the response isn't linear. If areal density of heat rejection was able to raise air temperatures this amount, then nobody would be able to go anywhere near a thermal power station without being vaporized.