Your reading comprehension is the problem here, not what they said.
The context of the comment was that rock was something people hadn’t experienced before, and that those perceptions changed with more exposure to the genre.
When they first heard Nirvana, their opinion was that it was hard rock, because it was the hardest rock they had heard by that point.
It’s a subjective recounting of their opinion when hearing something new, not an objective classification of Nirvana as hard rock.
Your reading comprehension is the problem here, not what they said.
The context of the comment was that rock was something people hadn’t experienced before, and that those perceptions changed with more exposure to the genre.
When they first heard Nirvana, their opinion was that it was hard rock, because it was the hardest rock they had heard by that point.
It’s a subjective recounting of their opinion when hearing something new, not an objective classification of Nirvana as hard rock.