That comes as a relief, as John hadn't wanted to furnish his highly technical explanation of Remy's powers. The explanation would have consisted of 'I don't know how it works, but he touches things and they explode'. The relief is short-lived, however, as seems to be a trend with Erik. The elephant in the room question flusters him just a little, that's pretty clear. Magneto had never asked. He's never had to articulate any reason for joining the Brotherhood, and he doesn't want to get all fanboy about it. So he does look away out of awkwardness, but immediately looks back, because he's not going to be hesitant or anything, that's not going to impress Erik.

"You're him... or the closest thing." John shrugs again, trying to act like it's not as important as it is to him, because he can't sort this out on the spot. "I'm not like, gonna follow you around if you don't want, that's fine, I'll just work with Remy and do my job at the newspaper or whatever. Maybe the Brotherhood isn't even necessary here, I don't know. It's just been my life for the past four years, so... whatever, I'm here if you need something set on fire." The self-deprecation there is a little grim.