How does CLASSPATH work?

As a result of this question

java.lang.NoClassDefFoundError with explicit CLASSPATH

It has emerged me a doubt. The Oracle documentation onCLASSPATH tells us:

The class path tells JDK tools and applications where to find third-party and user-defined classes -- that is, classes that are not Java extensions or part of the Java platform. The class path needs to find any classes you've compiled with the javac compiler -- its default is the current directory to conveniently enable those classes to be found ... Class paths to the .jar, .zip or .class files. Each classpath should end with a filename or directory depending on what you are setting the class path to:

• For a .jar or .zip file that contains .class files, the class path ends with the name of the .zip or .jar file.
• For .class files in an unnamed package, the class path ends with the directory that contains the .class files.
• For .class files in a named package, the class path ends with the directory that contains the "root" package (the first package in the full package name).
  
  Multiple path entries are separated by semi-colons.

However, from my experience, I have come to the conclusion that all the tutorials on the internet and the documentation itself are wrong .

The concrete case.

Let's put a minimal code file, which uses some external library:

import com.google.gson.Gson;

public class MCVE {
  public static void main( String [] args ) {
    System.out.println( " ***** Iniciando la prueba *****" );

    MCVE mcve = new MCVE( );
    String json = new Gson( ).toJson( mcve );
    System.out.println( json );

    System.out.println( " ***** Prueba terminada *****" );
  }
}

Likewise, a pom.xmlminimum, but that we copy the dependencies to a directory (in this case, target/libs):

<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>es.stackoverflow.com</groupId>
  <artifactId>MCVE</artifactId>
  <version>1.0</version>

  <properties>
    <maven.compiler.target>8</maven.compiler.target>
    <maven.compiler.source>8</maven.compiler.source>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <maven.test.skip>true</maven.test.skip>     
  </properties>
  <dependencies>
    <dependency>
          <!-- https://mvnrepository.com/artifact/com.google.code.gson/gson -->
          <groupId>com.google.code.gson</groupId>
          <artifactId>gson</artifactId>
          <version>2.8.5</version>
    </dependency>
  </dependencies>
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-jar-plugin</artifactId>
        <configuration>
          <archive>
            <manifest>
                <mainClass>MCVE</mainClass>
            </manifest>
          </archive>
        </configuration>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-dependency-plugin</artifactId>
        <executions>
          <execution>
            <id>copy-dependencies</id>
            <phase>prepare-package</phase>
            <goals>
              <goal>copy-dependencies</goal>
            </goals>
            <configuration>
              <outputDirectory>${project.build.directory}/libs</outputDirectory>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
</project>

All this placed in a more or less standard directory hierarchy:

/mcve
+-pom.xml
+-src
   +-main
      +-java
         +-MCVE.java

We compile it:

>mvn package

After which, our directory hierarchy contains:

/mcve
+-pom.xml
+-src/
| +-main/
| +-java/
| +-MCVE.java
+-target/
   +-MCVE-1.0.jar
      +-libs/
         +-gson-2.8.5.jar

Also, we look inside the .jar, the file MANIFEST.MF:

Manifest-Version: 1.0
Archiver-Version: Plexus Archiver
Built-By: root
Created-By: Apache Maven 3.6.3
Build-Jdk: 1.8.0_252-ea
Main-Class: MCVE

Now, we run it:

>cd target
>CLASSPATH='libs/' java -jar MCVE-1.0.jar

But it seems that he doesn't like it :

>java -jar MCVE-1.0.jar
***** Starting test *****
Exception in thread "main" java.lang.NoClassDefFoundError: com/google/gson/Gson
 at MCVE.main(MCVE.java: 9)
Caused by: java.lang.ClassNotFoundException: com.google.gson.Gson
 at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
 at sun .misc.Launcher$AppClassLoader.loadClass(Launcher.java:352)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
 ... 1 more

We continue testing all possible ways to indicate the CLASSPATH:

>CLASSPATH='libs' java -jar MCVE-1.0.jar
>CLASSPATH='/root/mcve/target/libs/' java -jar MCVE-1.0.jar
>CLASSPATH='/root/mcve/target/libs' java -jar MCVE-1.0.jar
>export CLASSPATH='/root/mcve/target/libs/'; java -jar MCVE-1.0.jar
>CLASSPATH='libs/gson-2.8.5.jar' java -jar MCVE-1.0.jar
>CLASSPATH='/root/mcve/target/libs/gson-2.8.5.jar' java -jar MCVE-1.0.jar
...
>java -cp 'libs/' -jar MCVE-1.0.jar
>java -cp 'libs/' -jar MCVE-1.0.jar
>java -cp '/root/mcve/target/libs/gson-2.8.5.jar' -jar MCVE-1.0.jar
...

In all cases I get the same exception.

In which authorized source is the behavior of java and CLASSPATH explained and detailed according to the results observed?