You may be right, because when you listen to it doesn't sound "seventies" like how how an Alan Parson produced album would sound.
That is mostly in part because of the lead guitarist, who instead of putting mic's in front of the speakers, would just plug the amplifiers directly into the soundboard, and use that to shape the tone and color of the music. That album changed how rock and metal would sound; listen the first Van Halen album to hear how they copied it.
Another album similar is Iron Maiden's "Somewhere In Time", which is sounds like nothing else out there. The best word I can think of is gigantic.