To reproduce:

Make a new Qt Quick 2 application using the template in Qt Creator. Add a file called e.g. Test.qml next to the main.qml. Reference this type from the main.qml.

Deploy and run the app on a device. You'll get an error message that the Test type is not available, but QML should be able to resolve it when it's next to the main.qml. If you look under android/assets in the project, you'll see that the file is deployed into assets.