Why is Guava's EventBus marked unstable in IntelliJ 2018.2?

20knots :

A new inspection was added in IntelliJ 2018.2 which should warn from unstable APIs: https://youtrack.jetbrains.com/issue/IDEA-159541.

This warning shows up for the Guava's EventBus. Why is this an unstable API?

JB Nizet :

Because the EventBus class is annotated as @Beta.

You'd have to ask the Guava project maintainers why a class that exists for 16 versions of Guava is still Beta, but it still is.