> As part of your employment agreement, Google most likely owns intellectual property (IP) you create while at the company. Because Google’s business interests are so wide and varied, this likely applies to any personal project you have. That includes new development on personal projects you created prior to employment at Google.

Just to be clear, it says "new" development while you're employed by Google, they don't claim to retroactively own your prior works pre-employment. I'm sure they ask you to declare it though so it's clear what you built before joining.