I beleive Michael stated once the next development cycle comes around he would look at it.
Bulkuploading and extra fields even the old extra 6 fields NEVER where pulled automatically. Its been that way forever. Its not like we changed anything with the addition of custom extra fields.
If you did bulkuploads with the old thing extra fields did not change between cat selection boxes as there has never been a third step that there would need to be to update all those selections again.