In Gradle 8 (build system) Kotlin DSL, should a convention plugin be defined under `buildSrc` or `build-convention` directory?

Question

I've seen both cases in official samples:

under buildSrc:

https://docs.gradle.org/current/samples/sample_convention_plugins.html

as:

.
├── buildSrc
│   ├── build.gradle.kts
│   ├── settings.gradle.kts
│   ├── src
│   │   ├── main
│   │   │   └── kotlin
│   │   │       ├── myproject.java-conventions.gradle.kts
│   │   │       └── myproject.library-conventions.gradle.kts

under build-convention:

https://docs.gradle.org/current/samples/sample_sharing_convention_plugins_with_build_logic.html

as:

.
├── application
│   ├── build.gradle.kts
│   └── src
│       └── main
│           └── java
│               └── org
│                   └── gradle
│                       └── sample
│                           └── app
│                               ├── Main.java
│                               └── MessageUtils.java
├── build-conventions
│   ├── build.gradle.kts
│   ├── settings.gradle.kts
│   └── src
│       └── main
│           └── kotlin
│               └── myproject.java-conventions.gradle.kts

Which one is "more" correct? Based on what evidence or theory?