It is to control pre-ignition and compensate for heat soak. The flame front travels faster with hotter air temps and leaner mixtures.
It would make more sense for it to happen under boost, but I guess its a certain factor of safety.

From megasquirt's megamanual:

IAT-based Fuel Correction
Some users have found that the ideal gas law calculation of air mass does not work especially well for them. This could be because the air entering the cylinder does not reflect the measured temperature. The IAT fuel correction table lets the user define a 6-element table of IAT (intake air temperature) corrections top the fuel amount.

• File: This offers the usual fetch, burn, and exit options.
• Tools/Curve Generate: This allows the user to generate a linear, exponential, or logarithmic curve automatically to fill in the 6-element table.

IAT-based Timing Retard
This is a table that is used to reduce the ignition advance at higher intake air temperatures. Because hot mixtures (typically from the heated air from a supercharger or turbocharger) burn more quickly and are more likely to detonate, reducing spark advance at higher intake air temperatures can help the engine to run better and avoid destructive detonation. The ten element MAT-based retard table lets you specify this reduced advance.