I'd phrase that a bit differently but the point is well taken. Airplanes do have panel lines. whether they are really visible at normal viewing distances is something else. I think many models over-emphasize the panel lines. On natural finish aircraft you can see the panel lines if you are close enough. At further distances you can make out some panels because of different alloys or surface treatments.
On painted aircraft the paint tends to fill in most panel lines, except for thos panels which are removable for normal surface. These can be emphasized if one does it lightly. Emphasizing panel lines is very much a case of less is better.
If you do heavily weather an aircraft or other vehicle, make sure everything is consistant. I have seen heavily weathered WW2 aircraft with pristine national markings, kill marks, and pristine shiny and clear canopies.