Curious as to what airline and at what airport? Usually pre-flight is before the plane taxis "from" the gate not when it arrives "at" the gate.
A plane lands, taxis to the gate. Passengers disembark, the plane gets cleaned and refueled, people on the ground checked it out, new passengers board (me), and it taxis from the gate. At no point did the pilots leave the airplane to "walk-around".