Kind-of. The basic idea of needing to be able to display both screens with the same tileset during screen transitions does exist. The game has a common sectio

Kind-of. The basic idea of needing to be able to display both screens with the same tileset during screen transitions does exist. The game has a common section, and a section that can vary by screen. However most screens just use the common section, with only some screens using the unique section. Between any two unique sections the game will have at least one screen that does not use that section of the tilemap. On screen transition, if the transitioned to screen needs a unique section, it is loaded, and then the screen starts to scroll. However the game will correctly handle going directly from one screen that uses the unique section to another. The only issue is that the old screen may look weird between when the new section is loaded, and scrolling has finished. So what is happening with death mountain ascent/descent? Well, the death mountain area actually uses a modified version of the global tileset. (And modified versions of certain global palette entries). Normally it is not possible to go from the rest of the overworld to death mountain or vice versa, except via a cave (and switching from underworld to overworld requires reloading the tilesets), or via flute (where the same occurs). The game lacks any code to modify the global part of the overworld tileset (and palettes) on a normal screen scroll transition, as that is never supposed to be needed in normal gameplay. (There are similar considerations about what enemies can appear on adjacent screens, due to needing to manage sprite tilesets.)