Apple has released the fourth beta of iOS 12.1.3 to developers & public beta testers.
At this time, there are no major changes and features to be found. The same is to be said about iOS 12.1.3 Beta 3, which was released only two days ago. We don't know why Apple has released another beta so quickly.
We'll check if any new features are found and will update this article.
We can expect iOS 12.1.3 to be released in the next few weeks to the public, with just bug fixes. The developer patch notes have no information in yet.
Updated: According to iupdate, Apple has implemented a behind-the-scenes feature that allows them to remotely disable the new force close app animation on iPhones in China that recently received it.