There is no consistency in how jpackage reports package build progress across supported platforms:

# macOS DMG:

[00:29:45.093] Creating DMG file: /test/output/SimplePackageTest-1.0.dmg.
...
[00:29:53.151] Result DMG installer for SimplePackageTest: /test/output/SimplePackageTest-1.0.dmg.
[00:29:53.151] Succeeded in building Mac DMG Package package

# macOS PKG:

[00:30:08.690] Succeeded in building Mac PKG Package package

# Linux DEB:

[23:56:12.787] Generating DEB for installer to: /test/output/simplepackagetest_1.0_amd64.deb.
...
[23:56:28.153] Succeeded in building DEB Bundle package

# Linux RPM:

[00:06:32.358] Generating RPM for installer to: test/output.
...
[00:07:19.044] Succeeded in building RPM Bundle package

# Windows MSI:

[00:44:03.570] Generating MSI: C:\\test\\output\\SimplePackageTest-1.0.msi.
...
[00:44:17.822] Succeeded in building MSI Installer Package package

# Windows EXE:

[00:44:40.513] Generating EXE for installer to: C:\\test\\output.
[00:44:41.127] Installer (.exe) saved to: C:\\test\\output
[00:44:41.129] Succeeded in building EXE Installer Package package

Multiple resources are used to create the above messages:

src/jdk.jpackage/linux/classes/jdk/jpackage/internal/resources/LinuxResources.properties:
  message.outputting-to-location=Generating DEB for installer to: {0}.
  message.output-to-location=Package (.deb) saved to: {0}.
  message.outputting-bundle-location=Generating RPM for installer to: {0}.
  message.output-bundle-location=Package (.rpm) saved to: {0}.

src/jdk.jpackage/macosx/classes/jdk/jpackage/internal/resources/MacResources.properties:
  message.building-dmg=Building DMG package for {0}.
  message.creating-dmg-file=Creating DMG file: {0}.
  message.output-to-location=Result DMG installer for {0}: {1}.
  message.building-pkg=Building PKG package for {0}.

src/jdk.jpackage/windows/classes/jdk/jpackage/internal/resources/WinResources.properties:
  message.outputting-to-location=Generating EXE for installer to: {0}.
  message.output-location=Installer (.exe) saved to: {0}
  message.generating-msi=Generating MSI: {0}.

On top of being inconsistent, it is a maintenance burden. Simplify it and replace platform-specific progress messages with shared ones.