A very important skill for Senior engineers not mentioned in the article is an ability to take the initiative on something. For example, when a dev sees a bug in an area of code they aren't responsible for and thinks "I'll raise an issue for that and mention it to the product manager so we can get it fixed" instead of "Oh, a bug", then they're starting to show that senior mindset. It's a desire to make the whole of the software good rather than just the little bit they work on good.