Thanks for the write up Luisma.
If I'm reading this correctly, the band did not want to release an album in 1986? They get pressured from EMI and they make a draft record that isn't a good enough follow up to Powerslave, then they change it and use best studio magic at the time to make it SciFi sounding in order to give it that "something special" a new Maiden album always had, up to that point?
Smith seems satisfied with the end product tho, because he picked it as one of his favourites (or his favourite) Maiden record in 2005 or so. His songs are probably true to his demos, which means it is the Harris songs that got overhauled. I always suspected that Harris doesn't like this period and this record, and that is the chief issue behind not ever playing ATG. Possibly he dumped the Dickinson track, to have enough runtime to rearrange and repolish his material. In the end the record wasn't universally acclaimed as TNOTB/PoM/PS so this decision might've been wrong.
Edit : just a note that I've read a french mag scan from 1986 with Dickinson interview, I don't speak French but I could recognize Dickinson is mentioning ATG as-is (8+ min track about an ancient warrior) and that he has a writing credit in the next sentence.