It's not 7 days from when you last connect it to a computer. It's 7 days since the phone was last unlocked.
“To improve security, for a locked iOS device to communicate with USB accessories you must connect an accessory via lightning connector to the device while unlocked – or enter your device passcode while connected – at least once a week.”
Because the quote says "enter your device passcode while connected"
= the device has to be connected while entering the pin.