Heck no, it doesn't matter-for me.
As an engineer (and I'd probably find this guy's work interesting, but that's because I'm a geek!) I would prefer a guy who isn't interested in my work, because I would rather talk about which politician's making a fool of himself, how we can achieve world peace, stuff like that, when I'm not at work. I have 40+ hours a week to talk about my job already.
Now, if I'm having coworker problems, I would like my SO to be supportive and be a sounding board for how to deal with people-but that's an occurence regardless of career, and that's more him having an interest in me.
It's weird to me that he'd want to take your friend on a tour, though. Particularly if he doesn't know her yet, and he wants to give her a tour already. He's allowed to give her a tour at all, if it's so top secret? Red flags-something sounds wrong about that to me!