We’re talking about two different notions of free-will. But let’s ignore that and focus on what you’re saying instead. The concept of “free-will” you speak of can be defined as “the ability to make decisions independently from what happened in the past”. If a human being can make decisions independently from what happened in the past (i.e. if his decisions cannot be predicted from prior events), then we can say that he has free-will.
Note that indeterminism is nothing more than “the doctrine that not all events are wholly determined by antecedent causes”. Indeterminism really only opposes strict or hard deteriminism which is the idea that any portion of the universe can be predicted with 100% accuracy based on something that happened in the past. This means that indeterminism is perfectly compatible with other forms of determinism such as statistical determinism which is the idea that some or most but not all parts of the universe can be predicted with more than 50% accuracy based on something that happened in the past.
Since hard determinism requires that every part of the universe can be predicted with 100% accuracy based on something that happened in the past, it follows that the abovementioned notion of free-will is incompatible with it, for it requires the opposite of it. On the other hand, since statistical determinism has no such strict requirements, it follows that the concept of free-will we speak of is compatible with it.
The fact that we can say that such decisions are nonetheless caused by the subject has nothing to do with it. That would simply mean that the decision was created inside someone’s skull, not that it was caused by some prior event.