I assume it's benign neglect and different interpretations.
Kraft isn't exporting Vegemite to the US because it doesn't meet FDA regs on added folate.
A [link|http://www.news.com.au/story/0,23599,20641599-1702,00.html|news.com.au] story with quotes (cited by others).
My take: A person can bring Vegemite to the US, but the border patrol can seize it if they choose. They're just not "targeting" it.
FWIW.
Cheers,
Scott.