Okay. Workaround is as follows.
Create .inc file with repackager. Edit this file with notepad. Where it says Operating System, make sure that the language is 1033, not 2057.
For me this line is "OSInfo('Windows 2000','5.0.2195 Service Pack 3','1033')".
Then open this .inc with the legacy converter and run. All will work fine then. Clearly the converter doesn't pick up the language from the template, but rather uses the language specified in the OS.