Here's what you are missing. Impact sprinklers are horribly inefficient. They throw a lot of water out to the perimeter of a circle and almost nothing lands inside...unless you take a good half hour to fiddle with the stiff little adjustments on the things. I gave up on those about 30 years ago. I have tried the newer technology impact sprinklers and got the same miserable results.

Instead I have opted for an oscillator type sprinkler. I go with the "turbo" type and not the ones with the mechanical linkage. Mechanical linkage ones break sometimes in the box before you get home. The turbos work very well for years as long as you NEVER try to force the sprinkler to move by hand. That is a shortcut to the trash bin for turbos. With my hose and water pressure it takes a good 8 hours to fill a tuna can, but it is the most even sprinkle you can get.

I've never seen and "average recommendation of 1.5 inches per week," but I'm not surprised that is someone's opinion. About 15 years ago I worked/argued with a guy here on this forum who tried to tell me that deep and infrequent was much better watering plan than my daily regimen I had been doing. He convinced me and I've been advocating it ever since. There are many factors which go into watering including type of grass, type of soil, air temperature, humidity, wind, sunlight shade, cloudiness, length of grass, and some others. The predominant factor is the daily high temperature. Once you have what I'm about to explain then you can adjust for your situation.

Generally: when the temps are below 70 degrees, water deeply once every month. With temps between 70 and 80, water deeply once every 3 weeks. With temps in the 80s water deeply every 2 weeks. With temps in the 90s water deeply every week. With temps in the low hundreds, water once every 5 days. With temps from 105 to 110, water deeply every 4 days. With temps between 110 and 115, deep water alternating every 3-4 days. NOTE that you NEVER water every day even in Phoenix in the middle of summer. Note also that you always water a full inch. You have to take into consideration your soil, recent rains, and humidity. Those are the other factors bearing on the general deep and infrequent equation, but temp is the dominant factor by far.