When changing a pattern, it is always good to think thru what you are doing. Do I do that? Of course not. Worse, I didn't even read the instructions. In the pattern, the neck is supposed to be bound, so there is no seam allowance added there. I added 0.25 inches. On top of that, I added a neckband that is about 0.75 inches think. All that extra fabric produced a t-shirt with no neck hole. Well, it does have a neck hole, but the front covers the back part, and the back covers the front.
So if I want to add a neckband instead of binding, which I do, I will have to cut off the seam allowance and whatever width I decide to make the neckband. We shall see if I remember all this the next time I have 0.5 yards of knit fabric left over from one of my shirts.