It could be it has developed into a good forager. Like Balloonfish says, angels never stop looking for food. This one may be already full from from all the little tibits it finds in the tank and only strikes at feeding time because that is what it is supposed to do. After striking, it spits the food out because it is already full. I have a JD that does the same thing, but it keeps growing and stays active so it must be eating something!
Keep an eye on it to see how active it is and how it reacts with the other fish.
If you want to tempt it, I have never seen an angel in decent health turn down a baby guppy!