Siamo tutti connessi allo stesso WiFi, ma gli altri computer compaiono solo nel Finder quando sono vicini.
In base a questo articolo sulle basi di Mac , devi
(sottolineatura mia)
Qual è la spiegazione tecnica per questo requisito?
Utilizza il Bluetooth per cercare i dispositivi nelle vicinanze.
Puoi leggere ulteriori informazioni a riguardo su AppleInsider :
It should be understood that AirDrop is a proximity-limited technology, meaning that it will only work when two or more users are near each other. This is illustrated by the requirement that a compatible device, which will be limited to the iPhone 5 or later, fourth-generation iPad, iPad mini, and fifth-generation iPod touch, have both Bluetooth and Wi-Fi enabled.
When AirDrop is activated, it uses Bluetooth to scan for nearby devices that are advertising discoverability. User can elect to be seen by everyone, only by contact, or not at all if the feature is turned off.