Minor updates like iOS 16.4.1 are typically focused on bug fixes and security improvements. Since iOS 16.4 was released last week, some iPhone users complained about having to re-enter Wi-Fi passwords. There was also an issue with data failing to load in the Weather app, but Apple's system status page says that problem has now been resolved.
iOS 16.4.1 would be a stopgap update while iOS 16.5 remains in testing. Apple seeded the first beta of iOS 16.5 last week with a few minor changes, including the addition of a Sports tab in the Apple News app and the ability to start a screen recording with Siri. iOS 16.5 will likely be released to the public at some point in May.