Depends on who does the expecting...
...and what mood they are in. Certainly, the result was within the realms of some theory. At the other extreme was the possibility that the cometary material was so fluffy that it would do something like an aerogel capture, with little ejecta at all.
One theory about cometary jets holds that carbon monoxide is the fuel. If there were significant amounts of CO, then it would explain a big release like this. Time will tell (pretty quickly).