Most likely the areas in the shade stayed moist between waterings - increasing germination percent...

How often were you watering? Should be 4-8times per day....at short duration. MIght wanna top dress the sunny area with peat moss - its a good indicator of dryness as it lightens...also conserves moisture.

I'm watering the sh#t out of it and I don't think it's dried out at all but I guess it could use more. I was told not to use peat moss. Something about the soil acidity I think. I was thinking about using this "hydrocover triple threat" that is supposed to slowly release the moisture, but the seed wholesaler said I didn't need that either and I can't find any reviews on it so I haven't bothered.

I agree, you don't need the extra bells and whistles.

Where do you live?
What is your exact watering regimen? How often and for how long?

I'm in long branch, nj zone 7a. I have 6 sprinklers go for 20 minutes each one after the other starting at 9:30, 2, and 4. I also walk around and check throughout the day watering by hand, starting an extra round of sprinklers, or both. I'm confident nothing has dried out, yet this area of dense shade, which I've watered the least, looks the best. It's a beautiful almost fluorescent green.

Cut that time down to 5 minutes and see if the grass does a little better. You might put done some cat food or tuna cans to see how much moisture you're getting. Some of the high flow in-ground systems can put out a full in (filling the cans) in 20 minutes. For new seed or sod, you only need to moisten the surface of the soil, not drench to the depths.

If I was to reset the time I would go with 6:30, 12 noon, and 6:30 (breakfast, lunch, and dinner).

Thanks dchall I'll try that.I'm tempted to put down more seed where it looks thin but the seed store is so far away.