Having released iOS and iPadOS 13.4 on March 24 with big new features like trackpad and mouse support for iPads and iCloud folder sharing, Apple is moving on to its next minor release.
Apple released iOS 13.4.1 without a beta test, and then started realeasing beta versions of 13.4.5 that primarily included only bug fixes. On April 29, without ever releasing 13.4.5, Apple released what it calls “beta 3” of iOS 13.5. So Apple just renamed the usual 13.4.5 release with an upgraded version number as it now includes more significant features.