Idioms, phrasal verbs

[Dingu]

Hi, I'm new to this forum and this is my first article here. It's been more than a half way through reading a biography of Elon Musk and I'm sick of skipping through those idioms and grammars I could never lookup by googling. Here's one I'm stuck with. THe book is talking about recruiting process of SpaceX in this section.
"The reward for solving the puzzles, acting clever in interviews, and penning up a good essay is a meeting with Musk."
I kind of able to guess what that underlined phrase means, but when I google that up, I can't find nowhere any usage same as here. I'm serious about if that phrase is REALLY used between English native speakers, how do they feel reading such phrase, and how can it be implemented into other phrases.

ps. I think idioms are not part of grammar so I'm posting this here, but can this be in 'grammar help' forum or here's the most appropriate for this kind of English question?

[Joe]

pen = write

pen up = imprison, put in a pen
It’s the wrong word here

This has nothing to do with idioms, just vocabulary

This section is ok for your question

[Dingu]

Thanks Joe. It makes it clear, and it leaves me with a another problem. I'm reading this book written and published in America and there's funny word in the book. It'd be a struggle for ESL speaker to figure out what's happening there. For you as a native English speaker, how do you feel when you face with such wrong word usage or wrong grammar in a writing? Would you think 'there's stupid word there' and move on or would you ever think 'there's an interesting word there, is it something new I didn't know', and try googling it when taken even further?

[Joe]

It’s horses for courses

Sometimes I know for sure it’s a mistake or just nonsense and move on

Sometimes I’ll check, especially if it may be an Americanism that I don’t know

[Dingu]

I see it. Thanks a lot!