Ahoy uses this fact to connect Doom and Wolf3D (and co.) to other action RPGs that came before it. What does this mean? Probably nothing, as you can make any argument and provide equally valid evidence in either direction.
What genre Doom belongs to doesn't even matter as much (to me), since it contains influences from sources as varied as Action-horror like Evil Dead movies to bits of the Alien trilogy to its contemporaries, etcetera etcetera. What irks me is the people ignoring notable first-person perspective games before Doom or Wolf3D or Cata3D, as there are plenty.