My flight instructor always drilled the same thing, every time we flew twins. While it may be true for most recips, it's definitely not true for jet props. Some of them climb better on one engine, than recips on two. If you throttle back a bit most turboprops will easily get 1000 fpm on one, with very manageable yaw control.
In any event, both engines were probably powered in this crash. It's tough to fly when you can't see.
Roger on the turbine but I think the 310 has normally aspirated engines (in pilot talk).