Being asked for a demonstration of his sleeves is somehow both unexpected and inevitable at this point. Unfortunately he has no one but himself to blame for the fact that she feels impetuous enough to ask. And he is hardly going to deviate from his grudging tolerance of this conversation now. Giving his permission only to withdraw it in the next moment is simply not something he does, no matter how exasperated he feels.

But he's still not willing to hold out his arm to be inspected like wares at a market.

He deigns her outstretched arm with barely a glance. "Is this professional interest?" Do... whatever she is, have tailors? Her clothing seems complex enough. At least convince him this is educational in some manner.