[tobylane]

Within seven days of the last time you entered your pin, the USB port will function without requiring you to enter your pin.

[DavideNL]

Where did you get that info?

Because the quote says "enter your device passcode while connected"

= the device has to be connected while entering the pin.

[tobylane]

If it's been seven days since you unlocked the phone you will need to enter the device passcode while connected to the device, the prompt coming up because you connected it.