Honestly, I've never tried to lock up the tires on my Raptor at highway speeds, but I really doubt the stock brakes will lock the front tires at say 75 MPH. I know my older F150 wasn't even close to having enough braking power to lock up 33" tires at highway speeds. These brakes aren't much bigger and the tires are a whole lot heavier. If they can, I stand corrected.
Just because it has ABS doesn't mean it can lock up the front tires at high speeds on a high traction surface. There are plenty of low traction situations where ABS still functions fine, and it still will kick in for the rears a lot of times.