Hello larason2,
Yes -- that's correct -- in Hauptwerk v4 the _General object needed a Sys_ObjectID attribute set to 1, i.e. the following line would be included within the XML:
<Sys_ObjectID>1</Sys_ObjectID>
If you search the contents of 'Design tools | View Custom Organ Design Module ... format documentation' for 'HWv5' and 'HWv6' you will find a list of all new/changed/removed attributes in each of the versions.
(Caveat: we don't officially support v4 any longer, and back-porting organ definitions from one version to an older one is never officially supported either; ODF attributes may have changed or been migrated between versions.)