IIRC on this engine the gudgeon pin is a press fit into the conrod but floats in the piston; lubrication is most likely either via 'splash' or (if it's really fancy, which I doubt!) oiling jets that fire upward into the piston crown.
So your 2-second fitment window means getting the pin slipped through the piston and the conrod with the conrod roughly central before the conrod has chance to essentially glue itself to the pin, which would be bad if the pin was sticking half out of the piston skirt.
(Other designs would be 'fully floating' where the conrod has bearing clearance to the pin and the pin has clearance to the piston, with the pin retained in the piston by spiral clips, circlips or snap-rings, or where the rod floats on the pin but the pin is a press fit in the piston)