callbackFlow ExperimentalApi warning w/ kotlinx-coroutines 1.5.2

fun main() = runBlocking {
  callbackFlow<Unit> { send(Unit) }.collect {}

With implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.5.2' in my gradle dependencies, I’m seeing the following compiler warning:

This declaration is experimental and its usage should be marked with ‘@kotlinx.coroutines.ExperimentalCoroutinesApi’ or ‘@OptIn(kotlinx.coroutines.ExperimentalCoroutinesApi::class)’

This is present in the gradle build output, and in the IDE (which highlights the usage of callbackFlow).

According to the release notes, callbackFlow was promoted to stable API in v1.5.0, and when viewing the source code in the IDE, the definition of callbackFlow is not marked with @ExperimentalCoroutinesApi.

Is this expected?

ProducerScope (the receiver of the lambda) is marked as experimental.