Evolved Enderman are spawning using different mechanics that don't follow the normal behaviour of other mobs, which is probably the cause of all those reports of evolved enderman spawning even in properly lit areas (with the config of enderman spawning on day set to false).

How to reproduce:

In a flat world without structure generation (just to remove that factor from the equation), set the gamerule doDaylightCycle to false and set the time to 12500. Evolved enderman will spawn when normally mobs shouldn't spawn.

I haven't figured out yet what is the logic the mod's following but, a) is not the standard one b) it has something to do with block light level being incorrectly calculated.

I'm working on a fix, will PR if I find one.