Your instinct is understandable, but there is an important difference: wind chill does not make an ordinary thermometer read a lower temperature than the actual air temperature. It makes your skin cool faster because your skin is normally warmer than the surrounding air.
Suppose the air temperature is 5 °C.
Your skin might be around 30–35 °C. In still air, a thin layer of air next to your skin warms up and acts as insulation. Wind continually removes that warmed layer, so heat leaves your skin faster. Your sensory system interprets that increased heat loss as feeling colder. Hence 5 °C with a strong wind might have a “feels like” temperature around 0 °C.
But put a thermometer outside and wait for equilibrium. Eventually:
Still air: thermometer = 5 °C
Windy air: thermometer = 5 °C
The wind normally just makes the thermometer reach 5 °C faster. Once the sensor itself is at the same temperature as the surrounding air, there’s no temperature difference driving convective heat transfer, so wind cannot cool it below 5 °C.
That’s quite different from your skin because your body is continuously producing heat and supplying warm blood to the skin.
So why aspirate a weather-station thermometer?
The biggest problem with an outdoor temperature sensor isn’t usually wind. It’s radiation, particularly sunlight.
Imagine the real air temperature is 20 °C. Sunlight striking the thermometer might heat the sensor to 25 °C or more. A Stevenson screen shields it from direct and much of the indirect radiation while allowing air to circulate.
An aspirated radiation shield, such as the arrangement available on the Davis Vantage Pro2, goes further. A small fan continually draws representative outside air across the temperature sensor.
That helps prevent the sensor’s temperature being biased by solar heating of the sensor or shield. For example:
Actual air = 20.0 °C
Poorly ventilated sensor in sunshine = perhaps 22–25 °C
Well-shielded naturally ventilated sensor = close to 20 °C
Properly aspirated sensor = very close to 20 °C
There is one interesting exception to your argument: if the thermometer is wet, moving air really can make it colder than the air. That’s evaporative cooling—the principle of a wet-bulb thermometer. A wet sensor in 20 °C air could genuinely settle substantially below 20 °C.
So the people you were discussing this with were basically correct, but I’d phrase their explanation differently. Wind chill isn’t “not real.” The increased heat loss is very real. What isn’t real is a reduction in the actual air temperature. A dry thermometer at equilibrium doesn’t experience wind chill because, unlike your skin, it doesn’t have an internal heat source keeping it warmer than the air.
And that is precisely why aspirating your Vantage Pro2 is beneficial rather than introducing a wind-chill error.