The 43'9 is the part of the hull that touch the water. real length is 49'2
Not that this takes away from your boat but...
Per the specification:
Overall Length = 49'2"
(this generally means anchor pulpit to swim step)
Hull Length = 43' 9" (this generally means the length of the hull as it comes from the mold)
Generally the length you refered to in your post "the part of the hull that touch the water" is called the water line length, and will be somewhat less than the hull length.
Those are generally the way things are measured on boats.
Marketing is a whole different thing, as I posted above.
also, referencing Bakers post, I think he has the right idea.
Take two boats. One has a molded in swim step, and a molded in anchor pulpit, say 40' length.
The other has a bolted on swim step, and a bolted on anchor pulpit, say 36' hull, but with the swim step and anchor pulpit installed 40'.
The molded in manufacturer markets their boat as 40'. Should the manufacturer that bolts their swim step and anchor pulpit market their boat at 36' or 40'?
This difference in manufacturing process appears to give the advantage to the molded in manufacturer. I can see why the bolt on manufacturer would market based on OAL.