iOS 13.5 was released last week and it brought some necessary features for the ongoing coronavirus, such as support for the Exposure Notification API as well as optimising Face ID for users who are wearing masks, which is a lot of users now.
iOS 13.4.1 was released in early April and only really fixed a bug which prevented FaceTime calls between iOS 13 and devices on iOS 9.3.6 and earlier, users mistook this for forced obsolesce but this was just a bug.
iOS 13.4.1 is now no longer being signed, preventing downgrades and Apple has been doing this for years to prevent OS fragmentation and to encourage customers to keep their devices running the newer software – this isn’t forcing users to keep up to date, only to prevent downgrades.
