This is a topic I've always been interested in - H's rhythmic variation on certain riffs. Wicker Man is the same.
2 Minutes original version on the record is pretty much all down-strokes, mainly sticking to the A and D strings, only really extending to a full power chord vibrato on the 'D-C-D 5ths' end of each 'round' of the riff. But since H was 'allowed' to begin the song post reunion (as in, Janick started the song up until 2007...) he has begun to include up-strokes on the C5 and D5 chords which occur (if you count every 'stroke') on 3, 6, 9 and 12th 'stroke' of the riff - sorry

hard to explain - which I think gives it way more character and vibe. En vivo live recording really highlights this, if you watch the live video especially in the intro where it shows H playing.
H's rhythm is one of the hardest things to nail I think in terms of playing style - You look up any cover of 2MTM on Youtube and I guarantee they won't play that riff properly.. The vibrato of the 5th chords and the slight variation on the palm muting. It's both very simple and very complex at the same time.
Really just drives home how fucking sick Adrian Smith is at playing