Let us try some real numbers.
Say you set the heat to 73 and the cool to 74.
The heat comes on at 72 and runs till it hits 74.
The cool comes on at 75 and runs till it hits 73.
Usually, the temp continues to either climb or slide a little after the unit turns off.
If the heat cuts off at 74, but climbs to 75 before it stabilizes, the cool suddenly comes on.
If the cool cuts off at 73, but slides to 72 before it stabilizes, the heat suddenly comes on.
This is a no win situation. Even a 2* difference is cutting it close. I keep a 5* difference, and use a jacket if it gets cool. I use 69* for heat and 74* for cool.