Well, since they allow remote workers I think they are referring to remote Brazilian workers, but you are right if they are discriminating against local workers as well.
It could be something specific to Brazilian employment or finance law that affects remote workers based there. Perhaps the company is afraid of somehow having a tax nexus there, e.g. (perhaps, and this is just a theory) because they're already doing some sort of activity in Brazil and are nervous they are getting close to whatever standard Brazil has for tax presence.
That would explain why they are specifically concerned about Brazil and not, say, Peru or Singapore or anyplace else. It might be that they have assets in Brazil that they are concerned about getting caught up in a tax or labor dispute.