Craftworld Strategem; Forewarned

Just looking for opinions on this.

Forewarned states "Use this strategem immediately after your opponent sets up a unit that is arriving on the battlefield as reinforcements within sight of one of your <Craftworld> units that is itself within 6" of a friendly <Craftworld> Farseer."

Here's my question; what exactly counts as a unit arriving as reinforcements? Is it a) all units that are set up after deployment is over, or b) units that are paid for with reinforcement points?

My gut feeling is that option a is what's intended, but b seems to be the rule as written (and also makes it considerably weaker - how often do people use reinforcement points?), so I wanted to see how others here might have been interpreting it.

Core Rules, pg 3

Quote :

Reinforcements
Many units have the ability to be set up on the battlefield mid-turn, sometimes by using teleporters, grav chutes or other, more esoteric means. Typically, this happens at the end of the Movement phase, but it can also happen during other phases. Units that are set up in this manner cannot move or Advance further during the turn they arrive – their entire Movement phase is used in deploying to the battlefield – but they can otherwise act normally (shoot, charge, etc.) for the rest of their turn. Units that arrive as reinforcements count as having moved in their Movement phase for all rules purposes, such as shooting Heavy weapons. Any unit that has not arrived on the battlefield by the end of the battle counts as having been destroyed.

Well, that simplifies things. Not sure how I missed that - thanks.