The following video shows how to clear mainly older Air Max windows.

Use a blow drier.

(You may want to turn the sound off)

How far away is dependent on the blow drier (weaker -> closer), it is also recommended to keep the distance at first to avoid damages.

It also shows you:

Asking if a window is foggy is not really saying much about the wearability.
The seller might have just cleared it but the shoes may be unwearable noneoftheless.

It is a way to make a shoe more visually appealing, that’s it.

Yes, a foggy window CAN mean that a shoe may be unwearable, but a clear one doesn’t say it is.