Poser 6 did require that V4 (and other figures using ExP or INJ morph loading) be in the main Runtime unless you edited the files to set the correct paths. Poser 7 (Sr3, or with the search behaviour set to shallow) and later changed that so any Runtime would work, but at the time DAZ were aiming to support P6. Since they now test for P8, that could be updated of course (and the search for poser.exe dropped).