In talking about CORE and GMing on Twitter, I realized that the word "Experiential" is rarely present in the discourse. I think Narrativism has subclasses in it, and "Experientialism" is one of them. Another word for it might be "Phenomenological GMing" but that's an even tougher mouthful. The Experientialist GM is concerned with the Affect that play has upon you, and within you.
This is something that roleplaying does that no other artistic medium can do – to place you literally within a character, so that you not only “identify” with them, but emotionally resonate with them whenever dramatic actions are undertaken: The dice in your hand and the mechanical odds at the table literally echo the contingence of the hero's plan; the fictional stakes resonate on both levels.
Clearly there is more than one type of Narrativism. Because yes, I am interested in producing a narrative arc - that's why I tend to use the Harmon Circle, and wrote all that stuff about arcs in the DTGMG - but if you look at CORE Micro you don't see that, do you? That's because the pertinence of Narrative Arcs is GM-specific (or perhaps setting-specific). “Narrativism” can be about arc, but as a catch-all phrase for games it's very broad: it can just as easily be about theme, or style, or genre emulation, or author stance, or The Human Condition(TM).
The way I run, the intention is for the feelings and phenomena that arise within you to give purpose and direction to the decisions you make as a Player in the "Writers Room." So while my medium is the fiction itself, my actual goal is to evoke, convey, amplify, and interact with dramatic & meaningful emotional states in the real world. In you.
To put it another way: Although I obviously consider Arc to be important, the Experiential Affect I produce inside my Players' heads is even MORE important. If ever I must choose between breaking the Narrative Arc and breaking your immersion or emotional state, that's not even a choice. Your emotional state wins every time. It's one of the key reasons why CORE is so minimalistic and flexible: to allow the Story to turn on Meaning rather than rails or utter randomness. But note that CORE - certainly in its Micro edition - does almost nothing that says "This is how Tod does it." It doesn't "create" what I'm talking about. What it does do, however - what it was actually designed to do - is allow me to do Experientialist Narrativism with the absolute minimum friction.