If I prune a decision tree, does that make the resulting decision tree always more general than the original decision tree?
Are there examples where this is not the case?
If you filter something out by choosing one branch over another branch in the tree, the observations you did not choose are forever lost.
But to directly answer your question - no, it does not always make it more general. If you construct a tree where all the decision are exactly the same, then pruning does not make it more general.