I'll admit I haven't fully followed this back-and-forth.
But using GM fiat to resolve uncertainty doesn't seem outrageous to me. It depends on the RPG being played.
For instance, when the PCs in my Prince Valiant game sailed from France to Italy, it was uncertain who they might meet. I decided tha they met some pirates.
In my Classic Traveller game, when the PCs' starship suffered a misjump, it was uncertain where they would arrive. I decided that they arrived near the world of Ruskin (which I had rolled up some time before, and had sitting on my list of rolled-but-not-yet-placed-on-the-starmap worlds).
Nearly every time a test is failed in Torchbearer 2e play, it is uncertain whether the character will eke out a success but suffer a condition; or will suffer a twist. As GM, I decide; and I decide what the condition is, and what the twist is.