I think it looks more like a. prostrata. Prostrata tends to grow a bit more spread said:branch spacing is not an accurate way to tell the difference between prostrata and mille, spacing is based solely on water flow. High flow = condensed colony, low flow = spread out.
The only actual way to tell the diff between Prostrata and Millepora is to do a skeletal structure examination.
But to keep on topic, it is Millepora/prostrata