I can't disagree with any of Gerarddm's points, but I can't resist pointing out that what we're looking at here is a commentary on the changing state of the hobby. That Tamiya Scharnhorst represented the state of the art when it was originally released - about thirty years ago. (I think it came out in about 1977; maybe somebody can correct that.) I remember the review of it that Roger Chesnau, one of the most perceptive commentators in the ship modeling world, wrote for the British monthly Scale Models (which in those days was an extremely respectable source for such things). He commented that it was by far the best representation of the ship available in kit form. (Come to think of it, it probably still is. The only possible competition would be the 1/400 Heller version.) Outstanding points included the tiny anti-aircraft guns, the correctly-shaped Arado aircraft, and the masts and yards, which were almost to scale. And the sister Gneisenau kit correctly caught most of the differences between the two ships.
I believe the odd separate parts for the fore and after sections of the main deck were due to the shape of the hull. All the kits in the 1/700 "Waterline Series" (which in those days emanated from only four manufacturers: Tamiya, Hasegawa, Fujimi, and Aoshima) had one-piece hull and main deck parts. I'm not sure why that was considered important, but it apparently was. (Maybe they were trying to avoid seams at the edges of the deck.)
When the prototype ship had a bow and/or stern with a lot of overhang, that system didn't work; an accurate, one-piece casting of such a ship's hull and main deck would have been impossible to remove from the mold. Lots of kits in the "Waterline Series" had those separate deck sections at the bow and/or stern. (The original versions of the Yamato- and Iowa-class battleships come to mind.) Sometimes the break could be made to coincide with a breakwater or a section of superstructure, but if it couldn't, the modeler was indeed left with a difficult joint-filling problem. Eventually (I don't know why it took so long) the manufacturers figured out that casting the hull and deck separately, and making the hull in port and starboard halves - which they'd been doing for decades in larger scales - would solve the problem.
I may be sticking my neck out a little too far here, but I believe every 1/700 plastic kit until quite recently had raised lines representing the deck planks (if the real ship had a planked deck.) Some of the best resin manufacturers started countersinking 1/700 deck planks a few years ago, but I think the first examples from a plastic kit manufacturer were the new Tamiya Iowa-class battleships. That was, if I remember right, one of the kits' advertising points.
I just took a look at the new, revised Tamiya 1/700 Yamato. It has a one-piece hull-and-main-deck assembly, with a separate piece for the forecastle deck. (The joint comes conveniently at a breakwater.) And the "planking seams" are raised lines - extremely fine, but definitely raised rather than countersunk. The new Tamiya Missouri has separate port and starboard hull halves that have to be glued to the underside of the one-piece deck. The hull halves amount to thin strips of plastic; there are several "bulkheads" to help keep them from twisting out of shape.
I think it's really remarkable that these companies are revising their old kits. (It's perhaps worth comparing that Tamiya Scharnhorst to one of Revell's "current" kits: the 1/540 Missouri, which was originally released in 1952, was the first ship the company made, and is still being marketed as though it were a new product.) I hope Tamiya updates the Scharnhorst (along with the Gneisenau, King George V, Prince of Wales, and - my personal first choice - the Yorktown-class carriers, with their too-skinny islands.) But as for the original Scharnhorst kit - well, there are plenty worse.