Technically yes, it's a virtual device, but not all wifi hardware is capable of running two networks at the same time, Apple carefully selected the "usual" hardware to support this.

I think this is required for WiFi Direct and supported by all hardware?

Almost all Wi-Fi chipsets released in the last couple of years support this.

Many Windows and Android devices have been able to share a Wi-Fi network with other devices over another SSID, for example.

The only thing that's complicated is if a device needs to be a 802.11 station on one frequency/channel, and a host or P2P device on another, but that's almost always avoidable.

Everything else can be done purely in firmware or software.