They could cheat on charts to make it look like reaching a particular Fibs level, or completing a certain wave. When trading volume is low, it is easy to manipulate.
We want to see the actual moves at market open when volume is high to confirm or deny those patterns overnight.
Of course, sometimes, the trading volume after hours or overnight is very high (such as the case on liberation day), in those cases, we need to take afterhours pattern into consideration
