The airline is trying to bend the rules. In Article 5, you'll find that you are entitled to a reroute (5.1.b) *and* compensation (5.1.c). Reroute is a separate right than compensation.
Article 5.1.c.iii states you are entitled to compensation unless:
"they are informed of the cancellation less than seven days before the scheduled time of departure and are offered re-routing, allowing them to depart no more than one hour before the scheduled time of departure and to reach their final destination less than two hours after the scheduled time of arrival."
7.2.c says compensation may be halved if you arrive within four hours.
So if you arrive between two to four hours later, they owe you 300 Euros. More than four hours, they owe you 600 Euros. If they get you to your destination within two hours, they owe you nothing.