Comment by pjmlp

Nope, it is still Java, Kotlin is only the JetPack libraries.

https://source.android.com/docs/core/architecture

Also Koltin is meaningless without Java Virtual Machine, which is used to power most of Koltin existence[0], Gradle, Android Studio, thus the Android team keeps updating the Java support so that they don't lose access to the most used versions in Maven Central.

[0] - Kotlin Native and Kotlin Javascript are quite poor in available libraries