Have you crawled under there with a flashlight and looked for oil leaks on the oil pan, inside the inspection hole of the bell housing and bottom of the valve covers?
A lot of trucks with way more mileage don't lose any oil; there is no certain age or mileage as prerequisite. With that being said, some investigation wouldn't hurt. Perhaps even necessary as 150k is barely broken-in for a GEN3 power plant
All of the holes on the dipstick reading should always be covered so if you are showing more than 1 hole before an oil change I would suggest you check the level more frequently so that you aren't having these low-oil level problems.
My trucl hasn't been losing anything, anywhere since I bought it, but I still check the level on everything under the hood at least once a week. It's no strenuous task for me. It's good practice as this scenario proves. At least if you check it every week you will know the rate at which a system is losing fluids. If you ask me the dummy light means you are slacking, assuming no catastrophic failure, loose clamp, busted hose, maint/service fail, things of that nature.
Anyway, I'm going to check the different tech-literature for any mention of the dipstick indicators having any correlation with specific quantity, since that was your basic inquiry. I will also look for anything on the low level sensor.