They are in-flight towards Earth when they discover the humans have the capacity to lie (0). This forces an immediate reappraisal of their plans, which can only

They are in-flight towards Earth when they discover the humans have the capacity to lie (0). This forces an immediate reappraisal of their plans, which can only happen with FTL communication. Whether this changes their chance of success is certainly debatable, but it definitely changes their behavior. (0) note that AFAIR from reading book 1 just about a month ago, this is series-canon, not book-canon.