It is counterintuitive for traders to comprehend that forward selling by origin is a significant reason why spreads strengthen. It is an ideal condition when ICE spreads are in contango, for example, and the Real is weak as Brazil can take advantage of the premiums resulting in the forward months. But by selling a forward month, the ICE implied engine will connect the sold bid of the forward to the current bid of the front month causing the sale of a spread of the front to the forward. Of course, this situation does not exist presently as much as spreads are at a backwardation.
Conversely, the consumer sector doesn't care about the Real because they buy in $ mostly. But when they do buy forwards they will cause spreads to weaken as a result of the same mechanism.