First of all that is not a well-established origin story, but more like an urban legend. There are multiple conflicting versions of this same urban legend where multiple different restaurants claim to have invented the dish in the same way. And the restaurant chain (Moti Mahal) from one of these versions had been serving a virtually identical dish in their Delhi restaurant since the 1950s, ten years before any of these supposed origin stories. I will let you come to your own conclusions about what scope for authenticity that leaves for these stories.
>If I, as a Swedish person, move to the US and compose an awesome recipe for pizzaballs [2] where I combine Swedish meatballs with the American love for all things pizza [3] and it becomes a huge hit which is exported to the rest of the world, would that make the dish Swedish?
In your case at least you will be doing some "fusion" or "innovation" right? What exactly is the "fusion" or "innovation" in chicken tikka masala? Can anyone of sound mind actually claim that chicken tikka masala and butter chicken are two completely different dishes?
While we are making up examples on the spot, here is a more accurate one. If I start making pizzas in India and because mozzarella is hard to find here, just use processed cheese instead and may be put more chilis on top to suit Indian tastes, does the dish stop being pizza?
There has to be some reasonable limitation on how little you modify something before you get to call it a new "invention".