I didn't realize there was so much C and C++ in Android, I thought most of it was Java. Maybe they are just talking about the core system (including the Linux kernel and Java runtime) and not all the builtin apps.
Much of the graphics, camera, media, bluetooth, wifi, input handling, etc... stacks are native. There's a massive amount of native code in Android below the veneer of the Java API that apps are given.
Many of the higher level constructs are then in Java/Kotlin, though, like the builtin apps, system ui, activity & window managers, etc...
