Fair point, but again, hard rock and metal was not as clearly defined back in the 70s and 80s as they are now (overly so, IMO, but that's a thread for a different day).
The tension though (aka "difficult choice") is the whole point. Metal/Hard Rock really is interchangeable to my ears...up until thrash metal. Then I think it really separates. But all of that, and this entire Rushmore thing is so incredibly subjective.
Yeah, in the 70s KISS, Alice Cooper, AC/DC, Ted Nugent, Aerosmith, all kinds of stuff was being called "metal", and occasionally will still get called that way by some people. I think you start to get some separation on Black Sabbath's Master of Reality and Priest's Sin After Sin, but things don't really start taking off until the 80s. But even then it's tricky because if you bring in thrash, then it's blending into a different direction, into hardcore punk rather than hard rock.
In the end these things are bound to evolution and of limits being stretched. See it like sunset, when the sun goes down you can call it "dark". But then the night approaches and is even "darker", so what was arguabily "not-day", is certainly not as dark as the pitch black night.
Also, what's a "tall" building? the Great Pyramid was the tallest building for millennia. Then some gothic churches were. Then some skyscrapers were. Are gothic churches no longer tall? no, they are, but we have skyscrapers now that are taller than anything else.
Same with hard rock / metal. It was an evolution, it's hard to determine the exact moment something became "metal" just like it's hard to determine the precise moment when the day is no longer day, but night (that's what twilight is for, the passage between the two times of the day).
The 'tall building' analogy really hit the hammer on the nail.
Chuck Berry truly started it all. In the 60s, 'ERIC CLAPTON IS GOD' was spray painted on many a brick wall. George Harrison was innovative and would have made everyone's 'Mount' at the time. Beck, .....Page...and, of course, Hendrix.
70's: I'm prejudiced, but Brian May made sounds that no one had done before, and many emulated and semi copied in the years since. A shame that he wasn't allowed to shine more in the 80s. Who else can do BoRhap, the thirty seconds of 'You Take My Breath Away', 'Tie Your Mother Down', and then various rockers and the lovely 'a Winter's Tale' as the maestro of the fireplace. And who 'tapped' before EVH.
(we still bring out the photo with Brian on day one of our honeymoon in '02, and people may not know the name, but they recognize the face and the band
)
Iommi: love him to death, and the friendship between him and May is undeniable.
And, then there's JP, who's sometimes Queenish stylings attracted me to DT in the first place.
So...my five headed Rushmore would be Hendrix, Page, May, EVH, and Petrucci.