Fair points, see your argument there. I’d say the first two albums were just metal, not enough of the nu signifiers for me: scratching, ‘break it down’, face-breaking, white people rapping, huge unfocused angst. Although they did have drop tuning, the occasional rap-esque verse and lots of shouting so hmmm.
That said, the Manics were around during Britpop but weren’t Britpop - and there was tons of crossover with their fans and Blur/Pulp etc. (probably)
Dunno, if they ever were nu-metal, they’ve grown out of it by now surely