JPMS ServiceLoader does not work for me as expected

JPMS ServiceLoader does not work for me as expected.

I am trying to provide a desktop program as an executable jar with a default service, that can be overloaded by the individual user. A user provides their own service class and give their name as an argument on the commandline.

The service:

package eu.ngong.myService;

public interface MyService {
    public String name();
    public void doSomething();
}

The program together with the default service (the first lines in the if and the for are inserted for logging):

package eu.ngong.myService;

import java.util.ServiceLoader;

public class ServiceUser implements MyService {
    private static MyService myService = new ServiceUser();

    public static void main(String[] args) {
        if (args.length > 0) {
            System.out.println("trying to load " + args[0] + " envirionment.");
            ServiceLoader<MyService> myServices = ServiceLoader.load(MyService.class);
            for (MyService ms : myServices) {
                System.out.println(ms.name());
                if (ms.name().equalsIgnoreCase(args[0])) {
                    myService = ms;
                }
            }
        }
        myService.doSomething();
    }

    @Override
    public void doSomething() {
        System.out.println("The default service is acting.");
    }

    @Override
    public String name() {
        return "Default";
    }
}

Both collected in myService.jar with the main class of ServiceUser hosting the module-info.java

module MyService {
    exports eu.ngong.myService;
    provides eu.ngong.myService.MyService with eu.ngong.myService.ServiceUser;
}

An individual jar at a user may be

package eu.ngong.user1;
import eu.ngong.myService.MyService;
public class User1 implements MyService {

    @Override
    public String name() {
        return "User1";
    }

    @Override
    public void doSomething() {
        System.out.println("User1 is acting.");
    }

}

with the module-info.java

module User1 {
    requires MyService;
    provides eu.ngong.myService.MyService with eu.ngong.user1.User1;
}

However, running the program with

java -p ..\user1\user1.jar;myService.jar -jar myService.jar User1

leads only to the unexpected output

trying to load User1 environment.
The default service is acting.

While I expected with logging

trying to load User1 environment.
Default
User1
User1 is acting.

What did I miss?

java --show-module-resolution -p base-service/target/classes:user-service/target/classes --add-modules base.service,user.service -m base.service/base.service.ServiceUser user1 root base.service file://.../base-service/target/classes/ root user.service file://.../user-service/target/classes/ user.service requires base.service file://.../base-service/target/classes/ base.service binds user.service file://.../user-service/target/classes/ ... trying to load user1 environment. Services found : 2 User1 Default User1 is acting.

java --show-module-resolution -p base-service/target/base-service-1.0-SNAPSHOT.jar:user-service/target/user-service-1.0-SNAPSHOT.jar --add-modules base.service,user.service -m base.service/base.service.ServiceUser user1 root base.service file://...base-service/target/base-service-1.0-SNAPSHOT.jar automatic root user.service file://...user-service/target/user-service-1.0-SNAPSHOT.jar user.service requires base.service file://...base-service/target/base-service-1.0-SNAPSHOT.jar automatic ..... trying to load user1 environment. Services found : 1 User1 User1 is acting.

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