This is just theoretical pontification, but I think there is a respect in which size matters: heat dissipation. Suppose you have a sensor laminated to a heat sink. If you apply some flux density (power per unit area) to a very small area (as would happen with a phone camera), you can dissipate heat in three dimensions: back toward the heat sink and to the sides through the rest of the sensor. If, in contrast, you apply the same flux density to a large area, the edge effects matter less and you approach the limit where heat only dissipates straight back. This could have a dramatic effect on the temperature.

A similar effect happens in the kitchen. It's very easy to burn yourself by touching a large hot surface, but it's much harder to burn yourself by touching a hot pointy thing.