Part of what you might be experiencing is how you use the brake pedal. With ABS systems they want a slow steady brake pedal so the computer can do it thing. When you pump the brake pedal like you would do with non-ABS in slippery weather it confuses the computer and the ABS system.
I noticed when in Tow/Haul with my F350 if I just tapped the brakes it would shift but if a did a light steady it would slow without shifting. As I got into it harder it would shift. I suggest you try some different styles of braking and see what works for you.
Anyway, that is my experience,