Well, in practice I don't think that is correct.
I recently had a 3 hour delay (no big deal really) on a short haul flight. Prior to boarding I discreetly asked, firstly a member of the cabin crew, then the aircraft dispatcher what the reason was for the delay. Both of them said exactly the same thing, the aircraft was late back from a flight deck crew training excercise at Prestwick. On my return I wrote to the airline and asked out of curiousity, why no refreshments were provided. After several prompts they advised me that they were not obliged to provide any compensation as the delay was due to unscheduled aircraft safety checks. How can you prove or disprove that.
Also, I have seen an article in either todays or yesterdays Independent newspaper stating quite clearly that many airlines are simply ignoring the legislation.