The seed needs to be able to get down to the soil. If you dead grass was thin enough to allow that, then you luck out. If it was thick enough to mat down though, it is probably too thick for the seed to actually get down onto the soil. The easiest way to clear a smallish area is to use a string trimmer and chop it off to the soil level. It is really easy to rake up after that.

I was still watering. August got very hot as I recall. I think I watered for about 25 minutes , 3 times a week. I set the sprinkler system for early morning(5am) to prevent loss from the heat.

I believe it's a watering issue but hard to tell if it's too much or too little. If you get a disease that rots the roots, then the grass on top looks dry as if it was too little water...which it is up top but not below. The general hot weather watering guideline is 1 inch per week, applied all at one time. You're applying 3x per week. If you are applying on the order of 3 inches per week, then it is likely a disease issue. If you are watering less than an inch per week, then it is too little water. The way to find out how much water is going down is to put out cat food or tuna cans in the yard. Put some in the healthy looking area and some in the dry area. Turn on the system and see how much water you collect during a normal watering cycle. If the cans are almost full, you are watering way too much. If they are less than 1/3 full, then you are not watering enough. If you are getting about an inch per week, then the tune up would be to increase the duration of watering until you are getting a full inch, and at the same time back off on the frequency. By the way you're doing everything else right. Late spring fertilizer, check! Mowing high, check! Spot spraying weeds, check! Those are great pictures, too. Someone's been doing some homework.

I do see a slight rolling hill in the soil, with the top of it being on the line between your camera and the righthand edge of the shed. That could cause some waterlogging if the rainfall drains off there and the surrounding bits are a low point. I can't tell if it would get swampy, but it's probably a drainage point. As such, it should be mid-range challenging in terms of grass. I have a swale on the side of my property that gets rather moist in spring and fall, and dries out in summer. Due to the shorter roots on the grasses there, they shock more easily than the rest of the lawn. The designated ornamental tree spot has been a constant battle due to the moisture, and I finally just dropped in an old-fashioned lilac. I wouldn't hold my breath on getting the understory of that tree perfect, so I might be inclined to kill off the grass there and mulch the area around the tree. That doesn't look like thatch, it looks like dead grass. Whether the water killed it, or the soil chemistry is off, or there was a disease, I can't tell offhand. I think I'd consider a Logan Labs soil test here just to be sure.