I have a mechanical mitral valve (at age 50) and had AFIB a few years prior to that. When my AFIB developed, it never 'turned off' until I had an ablation.
Ablations are generally done through the veins so there is no comparison (surgically) to open heart work.
AV node ablation essentially destroys the heart's pacemaker (the AV node) so a permanent pacemaker is then a requirement.
The first ablation that I had would be called a pulmonary vein isolation. It was explained to me that during early embryonic development, when the heart cells split/fold to form our multi-chambered heart, cells in the vicinity of what becomes the AV node end up in the vicinity of the pulmonary veins. Hence the finding that a portion of AFIB can be resolved by isolating the pulmonary veins.
I would expect an electrophysiologist to be very involved in these discussions. Most ablations are scarring the heart tissue to block faulty flow of the heart electrical signals. (vs AV node ablation which is to stop the hearts electrical signal generator). These signals can be pretty difficult to discern and subtleties may not be evident via standard EKG. A few years after my mitral valve was replaced, I again developed the symptoms of AFIB. It felt just like AFIB to me. My kardiamobile indicated AFIB. Holter monitor indicated AFIB. Standard EKG indicated AFIB. However, when I was in the EP lab for another ablation, as soon as they hooked me up to their 25 lead EKG, they said "flutter". I had several flutter loops including one that had developed around a scar from the mitral valve insertion. So this ablation was actually to resolve some Atrial Flutter(s).
My experience may have little in common with your situation, but I hope it gives you a few more questions to ask or areas to investigate.