I haven't seen this particular situation identified as causing an illusion so I can only give you my opinion. For an aircraft on final approach there is always going to be a point on the runway at which the correct approach path intersects the runway surface. If you are sitting too low in the seat, that point is likely to be hidden under the nose, giving the impression that you are too high. If you are sitting too high in the seat, that point will appear further ahead of the nose giving the impression that you are too low. Large aircraft have a 'design eye position' that defines a particular spot in the cabin where the pilot's eye should be and the seat can be adjusted fore and aft and up and down to place the pilot's eye at that spot.

As I said, that's just my opinion so I'm interested to hear any other suggestions.

Bob