Considering GM had multiple lawsuits from idiots, they weren't able to put exact mileage for next oil change on the window sticker. Basically same fools that would try to sue for coffee being hot, so have to put on cup.."contents are hot"
It doesn't mean that you can't check the oil. My MINI doesn't have a dipstick....I even taught my wife to check the oil periodically. Just park on a level surface and press the button. They have to do this for the mutton heads that can't even open a hood