What canonical expert shared that information with you? In what part of canon law do you see a basis for the internal forum being a place where an individual pastor could essentially declare a marriage null, declare the remarriage as valid, and completely overstep the ruling of the external forum (AKA the tribunal)?

For those clucking on and on about the internal forum I don't really think they've thought through what they mean when they make use of that canonical provision. The internal forum is not just a place where a pastor would say "Voila, it's ok to go to communion now."

It's a juridical space which in the way you seem to understand it would run in direct opposition to the primary juridical element at work in these scenarios, the diocesan tribunal, the external forum.