Is Recall always exhausted?

No, recall does not inherently exhaust a unit.

According to Rule 453: "Recalls do not affect the state of the Permanent being recalled."

When a unit is recalled, it returns to your base in the exact same state (ready or exhausted) that it was in before it was recalled. A unit only becomes exhausted during a recall if the specific card effect that triggers the recall explicitly states to "recall [the unit] exhausted."