IOS 17.2.1 would likely be a minor update with fixes for bugs and/or security vulnerabilities. Our logs have revealed the existence of several iOS 17 versions before Apple released them, including iOS 17.0.3, iOS 17.1.1, and iOS 17.1.2.
Apple appears to be internally testing an iOS 17.2.1 update for the iPhone, based on evidence of the software in our website's analytics logs this week.