2 hours vs 1 hour might not make that much difference.
But coupled with a lower mash temperature, such as 148, certainly could.
While Alpha Amylase will be slower acting, it will act, and that will expose additional molecules to Beta Amylase.
1.5 quarts / 1Lb is not a thin mash. 1.25 - 1.5 is a "normal" mash when using a cooler (at least in many parts of the USA).
Mashes at 2+/1 may extract more sugars than the traditional 1.25/1