Bad design. BAD.

Yeah, they need to make their design responsive so it stays within the wordpress column like a well-behaved metabox should.

We’d also like to see this addressed. Not sure they monitor the forum here so someone might have to post it on Github: https://github.com/Yoast/wordpress-seo/issues

If you want to reign the box in and can add styles to your admin side, you can add the following:

#snippet_preview {
	width: 280px;
}

This won’t solve side-scrolling in the box but at least should keep your box from going over other elements from mobile to desktop sizes.

I’ll leave it up to Yoast to do a more thorough job.

A bug report is currently open for this issue. If you would like to follow the progress of the report, you can do that here: https://github.com/Yoast/wordpress-seo/issues/3468