1. I have created a new testcase to list all service providers for particular service interface.

2. Please find the attachment for three jars and javapackager log.
     a. com.shape.serviceinterface.jar
     b. com.shape.serviceprovider.circle.jar
     c. com.shape.serviceprovider.rectangle.jar

where "com.shape.serviceinterface.jar" contains service interface defined along with main class ShapeMainClass for entire Application.

"com.shape.serviceprovider.circle.jar" and "com.shape.serviceprovider.rectange.jar" are service providers for service interface.

3. ISSUE:
please check the following snippet in log.
<snippet>

INFO: Running command: [D:\Downloads\jdk-9_windows-x64_bin_101_jan20\jdk-9\bin\javapackager, -deploy, -verbose, -outdir, D:\TEMP\testBundlerWorkDir1148308311129
415526, -outfile, test, -native, exe, -name, ServiceList, -linkmodulepath, D:\Downloads\jdk-9_windows-x64_bin_101_jan20\jdk-9\jmods, -srcdir, D:\TEMP\testBundle
rWorkDir1148308311129415526\jars, -srcfiles, com.shape.serviceprovider.rectangle.jar;com.shape.serviceprovider.circle.jar;com.shape.serviceinterface.jar, -BMain
 Jar Classpath=com.shape.serviceinterface.jar;com.shape.serviceprovider.circle.jar;com.shape.serviceprovider.rectangle.jar, -detectmodules, -BMain Jar=RelativeF
ileSet{basedir:D:\TEMP\testBundlerWorkDir1148308311129415526\jars, files:[com.shape.serviceinterface.jar]}, -appclass, com.shape.serviceprovider.Rectangle]

</snippet>

In the above snippet u can see "-BmainJar" is pointing to jar file "com.shape.serviceinterface.jar" where as
"-appclass, com.shape.serviceprovider.Rectangle" is pointing to a class available in "com.shape.serviceprovider.rectangle.jar"

NOTE:
1. One point i want to emphasize is all three jars having MainClass attribute filled with classes available in respective jar.
2. "-name" argument is not passed to Javapackager, so it looks like AppName is picked from -appclass value.