We just noticed that languages marked as "disabled" can still be used if the "Default Language" is set to "Device Language". This is rather problematic, as we were using the "disabled" flag as a way of keeping the language in our project without making it available (because it is still in development). It looks like the code to select a startup language doesn't check if the language is enabled or not.
Is this the intended behavior?
Setting "Default Language" to "First in List (English)" is a sufficient workaround for now, as we only support English. Once we have some published languages and others still in development however, this won't be a suitable workaround.