If this effect affects all stars of the same mass in the same way, we would have nothing to compare them to. We do know more massive stars evolve much faster, and burn their nuclear fuel much more quickly, but that is already known to be the result the extra mass has on gravity, pressure, density, etc. And there are other factors involved, too, such as the percentage of metals (non-H or He) in the stars initial composition. For example, even a slightly higher concentration of heavy elements in the star greatly affects the opacity of the plasma, which alters the evolution quite substantially. This effect, and the exceedingly steep slope of the observed mass-luminosity function, would tend to mask this proposed phenomenon even if it did exist.

Stellar evolution is fairly well understood in its broad outline, but it is based as much on empirical observations as it is theory. We also know initilal mass is the single most important factor in determining that evolution, so any change added by this proposed fine structure variation would be masked by the fact the star is heavier in the first place. It would simply recalibrate the H-R diagram, not distort it beyond recognition.

What I feel is the biggest obstacle for this hypothesis is that any variations in fundamental physical constants might not just alter reaction rates, it might stop them from occurring altogether! Still, this is exciting news, if the laws of nature do indeed change in high gravity fields, it would mean that physics is not the same everywhere, in fact, that it varies all over the place. That is staggering in its implications.