Some might have different information about this, but as far as I see it, a smaller tire (less diameter) is easier to lock, and a bigger tire (larger diameter) is harder to lock. At some point if the tire get big enough you will not even be able to hold the car still in a hill no matter how hard to step on the brake pedal.
So, this is what first comes to my mind, that the 14 inch tires was larger in diameter than the 13 inch tires, and therefore when you hit the brake pedal with the smaller tires they tended to lock easier, and when the tire got a little bigger it was easier for your foot to control it since it as you said was a panic braking and you had less time to think and control your muscles in the leg.
This is my thought if this is the only thing that was changed. I really struggle seing it being a result of just 14 inch rims compared to 13 inch rims.