HI There,
The purpose of the tapioca is to provide a thickening agent that will gel up the fruit juices. The cooked version of tapioca does that automatically - the instant version requires no cooking and, in my opinion, won't be able to do it's job because it doesn't require cooking.

Of course, we won't know for sure unless we try - so you might want to experiment and make a discovery, if you are willing to risk your berries and your time. But, if it's a pie for a special occasion and has to be good right out of the oven, I wouldn't take the chance.