So using this, it would be possible for a player to select a resolution from this list, and the game update its display to reflect that decision?
It is possible to develop exactly that, yes. But the provided script just does the first, most important step for you: It lists resolutions that you can be sure of to be supported as fullscreen modes. All you have to do is this:
1) Offer the player the list to choose one of the resolutions.
2) Set the window to this resolution.
3) Switch fullscreen on.
Of course, you still have to decide what to do with the layout (stretching, black bars, zooming, etc.)
But without that list, you couldn't offer different fullscreen modes at all (apart from the current desktop resolution). So, the most important part is ready to go, but you still have to program all the details.