The London and New York overlap is the most quoted window in retail trading, and for a reasonable structural reason: two of the largest pools of currency liquidity are active at the same time.
What that overlap does not guarantee is direction. Higher participation tends to narrow quoted spreads and increase the pace of price discovery, but the underlying driver still comes from positioning, data and policy expectations.
A practical approach is to treat overlaps as a filter for when your strategy is allowed to operate, not as a signal in itself.