There is not really this "one" specification but rather a list of them. A very good source is still this book and for your question this chapter: https://books.sonatype.com/mvnex-book/reference/simple-project-sect-simple-core.html#:\~:text=Maven%20coordinates%20define%20a%20set,look%20at%20the%20following%20POM.&text=We've%20highlighted%20the%20Maven,%2C%20artifactId%20%2C%20version%20and%20packaging%20.
In general, in case of artifact identity, think more in the repository path layout that is created. This is based on literal string values and not abstract versions.

ComparableVersion is used for sorting version and version ranges, but they won't be resolved as the same artifact. As a test, create these artifacts with different numbers yourself and then look at your local repository (https://maven.apache.org/repository/layout.html). You will discover the different versions in different folders.