Asked my colleague, Mark O'Brien, who focuses on spreads for some feedback, hope this helps!
The NYMEX / Henry Hub Natural Gas spread (using the January contracts in this example) is primarily used as a hedge against price disparities between the two contracts, rather than a directional play, so it’s not prominently traded among speculative traders who typically employ spreads to take a directional approach in a given market or sector. Even inter-market spreads, i.e. ↑RBOB / ↓USLD, or ↑RBOB / ↓ Crude Oil benefit or lose based on both contracts’ similar movement up or down, just as a typical calendar spread would, i.e. ↑ Jan. NG / ↓ April NG.
Good general article by Mark at:
https://www.cannontrading.com/tools/the-seasons-of-the-futures-market