Is there a reason to use System.import when renderModernChunks is set to false?

[Schmale97]

I am trying to use the legacy plugin alongside another plugin vite-plugin-single-file (with bundles all code into the index.html) due does some specific requirements enforce by the hardware I am trying to use. However, due to the legacy code being partially loaded with System.import the single file plugin is unable to bundle it. I have raised an issue against plugin, but just wanted to check if there was a reason why the system.import was needed when only the legacy chunks are being rendered.