--with-import-modules option was used in JDK 9/10 for co-bundling JavaFX with the JDK. It seems this configure option is still in use, by some.

One aspect to this that should be re-visited is the code in make/common/Modules.gmk to map the modules to the boot or platform class loaders. If an imported module is mapped to the boot or platform class loader then it results in a different mapping to what would be done when creating the run-time image with jlink - with jlink, the javafx.* modules would be mapped to the application class loader.

A second aspect to this is that imported modules should probably be added to UPGRADEABLE_PLATFORM_MODULES as they aren't strongly tied to the platform/JDK modules.