He's always done that, even as a young man with White Spirit and Gillan.
Let him, the Iron Maiden fans love him for it and the other two guitarists can't really be bothered with stage moves (at the same time their duo-chugging-the-riffs gives Janick some athletic freedom). Quite a few of those moves are actually typical Blackmore gyrations (who borrowed his share from Hendrix it has to be said), the type you would also see with little Yngwie in the 80ies. Gers is a Blackmore nut - as you cannot only see, but also hear.
Iron Maiden has - in any incarnation - always been
either cringeworthy
or disarmingly down to earth and a band of the people, choose your sides, gentlemen! You're just so harsh on them, Rob, because you have the "estranged lover-syndrome" as a former fan.
I always found them a little naff, even when they were still opening for Priest, but they haven't become any naffer over the decades. Just consistenly a little naff, but endearingly so.
Oh my,
Iron Maiden (the song) is not exactly one of their more noteworthy compositions even if you mean well with them.
It sounds just like it came out of the rehearsal space it did emanate from. At this point, Steve Harris was no Brian Wilson (and judging from the backing vocals still isn't).