Since DigitalOcean will ignore it, you can set it to whatever value you’d like. The value unused in the example code makes it clear that you’re not using it.

I've edited the title slightly to make the intent of the question more obvious.

I like this approach more because I can scan the code that renders the Box component and easily spot that it takes two children. If the Box took any props, they'd be within the opening <Box> tag, and they would be distinct from any children props.

The link name is not very helpful, it doesn’t explain what it does very well.

One last bonus: CSS variables can be written in a way that makes it easier for human programmers to understand. If you just see hex code #93e9be, you won’t know what color it produces, while --brand-green makes clear the purpose of the variable.