Pressure to the rod is both pump and centrifugal, but centrifugal dominates.
If the cam bearing is trash or using a full grooved cam, oil may "skip" the mains and go straight toward the cam/heads.There would be a lack of pressure caused by a lack of restriction down stream (cam or head). Even still, when the rod feed passage aligns with the oil feed from the block it will fill no matter what - path of least resistance. Once it's full, centrifugal effects will force it to the rods throughout the rotation.
Damage to #2 and #4 caused by the trashed bearings or full groove cam will likely not happen at high revs, but when warm and at moderate load. Without adequate pressure to build the film, the bearings will heat and fail.
So theoretically at least, it seems possible to trash the mains and not rods. High revs, however, will trash rods and likely also adjusters and pushrods (lack of dwell at the cam causing a lack of supply to the heads).