For the sake of pacing and simplicity, this story glosses over the option to simply not do anything resembling acting. A player could simply say things like "I ask about the goblin attacks".
That might not fly in every gaming group. People might not think that's fun, the Game Master might insist players act some things out, etc. It's all going to depend on the dynamic of the group.
When you're Nanase in a comic shop and dating the GM, however, you can PROBABLY get away with playing however you want.
But getting into that would slow everything down without changing anything, or revealing anything about Nanase that won't be demonstrated in other ways, so they're just going to compare it to improv acting.
For anyone wondering what Nanase would say to a "just don't act" suggestion, however, Nanase wants to play as well as possible to support Ellen, and she considers the acting part mandatory because of that.
(I should note that I don't think there's anything wrong with playing without "acting". Play the game how it's fun to play for you. This is just how Nanase feels about herself in this exact scenario.)