Recently, Apple released the third beta of macOS 10.14.4, but there are no other betas for iOS, watchOS and tvOS alongside the release. Apple typically releases betas for all four Apple software categories simultaneously for every release, but some betas are released hours apart.
The reason Apple only released a macOS beta today is the features. The features and changes reflect similarly to the iOS 12.2 beta, which includes Canadian support for Apple News in French and English, along with smart TV control in the Home app. These are the only major changes in this beta of macOS.
Apple should be pushing the other betas to release at the end of February or early March. These betas are due for their official spring release on March 25, 2019. They’d only made the macOS 10.14.4 beta 3 similar to the iOS 12.2 beta though. Apple is still working on the features of the next iOS, watchOS and tvOS betas, which could be rolling out soon.