Yeah, I was hoping for more detail as well. I'm guessing they did something similar to what I did to make my Pi control computers.[0]
The Raspberry Pi 4 can emulate a USB keyboard and mouse, and there are inexpensive adapters that allow it to capture display output. You can also hook it up to a relay to cycle power for an external device.
As others have pointed out, keyboard / mouse emulation is pretty useful, but it's also quite quirky.
We use MDM to automate configuration delivery as much as possible, I think it's been mentioned as well (although we're not zero touch yet).
You might want to look at Asahi Linux's Central Scrutinizer for some insights on the fancier stuff that can be done over the USB-C port.
