But my big move

Is “begin a new round” an action someone can do though? Might be better to just rename “reset the board” to “begin a new round”.

If it’s defined as a step in an atomic action, and that atomic action can be undertaken, then yes, the step is by definition an action one can undertake as well.

I mean, an Atomic Action may be itself an action that can be undertaken, but that doesn’t necessarily mean that all steps of an atomic action are themselves actions that can be undertaken. The rules specifically cover the case where a player “arrives at a step in an Atomic Action and they cannot perform that step”. So when someone gets to the step that directs them to “Begin a new round”, what are they actually meant to do?

Zack, by that logic, players can’t do any of the steps in the atomic action as it stands, because it’s not defined elsewhere that they can reset the grid to a size or redraw the board or set the cells to blank. “Begin a new round” has a plain English meaning. It means that the player has made a new round begin.