Ideally, it would be wonderful to layer each restoration so as to perfectly match the shade of the adjacent teeth. I cannot speak for your dentist and about why he chose to use an A2 shade for your composite resin. It is not incorrect to do so, by the way. Perhaps he considered the molar a posterior tooth not in need of very detailed aesthetics. Optimally, yes, the tooth would be restored with multiple layers of composite, each meant to resemble the natural hue of the original molar's surfaces. I would ask your dentist this question. The most important aspects of this restoration should be the occlusion, form, and interproximal
contacts. When optimally finished, these are what give the resin the best prognosis.