Dependency injection at Singleton instance with hilt-android

Have a question while using hilt-android.
And I'm making some network module with retrofit, and handling with hilt.

@InstallIn(SingletonComponent::class)
object NetworkModule {    

    @Singleton
    @Provides
    fun provideBaseRetrofit(
      @BaseHttpClient
      client: OkHttpClient): Retrofit {
        val builder =
          Retrofit.Builder()
            .baseUrl(URL.Server.baseURL)
            .addCallAdapterFactory(ApiResponseCallAdapterFactory.create())
            .addConverterFactory(json.asConverterFactory("application/json".toMediaType()))
            .client(client)
            .build()
        
        return builder
    }

    @BaseHttpClient
    @Provides
    fun provideDefaultClient(
      @BaseRequestIntercept
      requestInterceptor: Interceptor,
      @BaseResponse
      responseInterceptor: Interceptor,
      @Logging
      logging: Interceptor): OkHttpClient {
        return DefaultHttpClient().newBuilder().apply {
            addInterceptor(requestInterceptor)
            addInterceptor(responseInterceptor)
            addInterceptor(logging)
        }.build()
    }
}

@Module
@InstallIn(SingletonComponent::class)
abstract class InterceptorModules {
    @BaseRequestIntercept
    @Binds
    abstract fun bindRequestInterceptor(request: RequestInterceptor): Interceptor
    
    @BaseResponse
    @Binds
    abstract fun bindResponseInterceptor(response: ResponseInterceptor): Interceptor
}

At this point, my question is, @singleton annotation.

At first, I attach singleton annotation to every single object, such as httpClient/requestInterceptor/responseInterceptor

However, the object's hashcode doesn't change even I remove annotation.
(Except retrofit, I remain singleton annotation to retrofit)

And my assume is, the singleton annotation only needs most upper instance.
like...

Intercept(not singleton) -> okhttp(not singleton) -> retrofit (singleton)

Why I though like this, retrofit is a singleton instance. Instance will not change so that It'll not make any other dependency object while application is living.

But I have no idea that my assume is correct, so I ask you guys...

Every example what I refer to, always attach @singleton annotation to every single provides class..

Is my approach wrong?

Thanks in advance!!!