Domestic content regulations.
If enough work is done in the US on rough parts brought in from Brazil, they don't have to mark it as an import. If they bring it in as a finished product, or one with only a little final work left to be done at SA, they do. Don't jump to conclusions, some are marked Brazil under a grip. Don't worry about it, the Brazilian guns are fine, it is just easier for them to do the lower volume guns at Geneseo.