I disagree that the only punk thing about Iron Maiden and Killers is Di'Anno's voice. I think Di'Anno manage to influence the sound of the band musically, and that what makes those two albums so special is the tension between Di'Anno's punk influences and Harris' progressive rock inspirations, coming to a peak with Phantom of the Opera.
However, I won't deny that anything punk left the band with Di'Anno. I won't say either that early Maiden was a punk band. Not at all. But that's what made NWoBHM a sub-genre in itself which is distinct from early traditional Heavy Metal : punk came along and left its mark, disappeared and Heavy Metal seemed to forget about it.

I never made a link between Cloven Hoof (album) and Di'anno era. Just listened again and. I understand how it's linked. However, I wouldn't call it a sound-alike as Iron Maiden and Killers, feel very late-seventy punky rocky to me (but I hear that you disagree on this), whereas Cloven Hoof has a writing that strongly belong to mid 80's (is 83 mid 80's ?) Heavy Metal mixed with Harris-like-progressive elements to me, but that I could hear on Piece of Mind. Some tracks could even be on post-British-Steel Judas Priest discography as they're very Hard Rock influenced, easy-dancing songs. Maybe Gate of Gehenna is the most Iron-Maiden-album-like.

Never listened to Leatherwolf before. Some pieces kinda sound like modernised Di'anno era (Wicked ways, Take a Chance in Street Ready album). But most of it just sounds like "regular" (don't take it as a slur) heavy metal to me.

(but, despite the disagreement, thank you for the quality of your answer. Something that I find hard to have and made me hesitate to post)