I don't mind harsh feedback. Its always a constructive
When falling and jumping the player adopts the same collision mask as ducking. This was a fix to a problem where the player was getting stuck on ceilings and walls if doing power jumps because to perform a power jump the player would go from duck collision mask to standing collision mask thus jutting its collision mask inside walls. In that case you are correct, the collision mask of falling state does not envelop the head. Only from the neck down.
Also, the spikes have a smaller collision mask. If the spikes had a precise collision mask the game would be literally unbeatable.