Your “very limited” understanding is right on my FRiend! There are a great many things that could still go wrong with this.
The flow very likely IS behind the pipe (outside the casing) but IS entering the well at some point (very likely through a liner lap). If that point is far enough down it doesn’t matter but if it isn’t that is really bad news!
Secondly, they must be careful in pumping so as to not overpressure and fracture the formation as that would also be very bad.
And thirdly, Even if the current operation is completely successful the relief wells will still have to be completed in order for this thing to be made safe.
What odds do you give this attempt?