Notso, I think the issue is a little more complicated than that, though you're on the right track.
In reference to the cross section profile mentioned above, you could think of an aircraft cross section this way.
Suppose you had a very large thin white screen and you mentally "passed" an aircraft through it on an axis perpendicular to the screen, so that the only thing that showed up on the screen, was the immediate cross section of the aircraft that happens to be in the "plane" of the screen. Suppose you could stop the "passage" of the aircraft through the screen at any point and measure the area of the aircraft's cross section.
Now think of the screen as representing a cross section of air that is being disturbed by the aircraft passing through it.
The air next to the "edge" of the aircraft's cross section, has to move "in" or "out", meaning "towards" or "away" from the center of the cross section as the aircraft passes through. BTW, this axis we're discussing represents the fuselage cross section, but the wing also has it's own central axis and cross section as well.
A fuselage design that has an abrupt change in cross section, causes a rapid acceleration of the surrounding air (and airflow) either "towards" or "away" from the cross section center, to either move out of the way or to fill the void (vacuum) created by the passage of the aircraft.
As an aircraft approaches transonic speeds, an abrupt change in cross section can cause the local airflow to go supersonic as it reacts to the abrupt change in cross section. The local shock waves created by this causes shock drag (i.e. transonic drag), and it can get very pronounced if the aircraft tries to go any faster.
A design that is carefully "area ruled" can delay the onset of transonic drag as it flies faster and faster, by delaying the onset of these local shock waves created by any abrupt changes in cross section.
The wing cross section (or profile) is a different animal in regards to transonic drag, and I know even this explanation is somewhat oversimplified. I'm not an expert here, so any corrections are welcome.