I’m not sure who wrote that, but compose can be rendered and tested in either a robolectric or instrumentation test environment.
The main difference is that robolectric is a simulated headless environment that does not draw to the screen and thus doesn’t require an actual device/emulator.
Instrumented tests run on a device/emulator, so the range of things you might test with them is different that what you might test in robolectric environment.