Some additional context on this: We found out that previously the math was flawed in that a champion's model size was taken into consideration only if the missile was hitting from the side, but not from the front. This means that previously if you shoot a skillshot right at an enemy, it would only hit when it hit the center of the target; but if you aim it at target's side it would hit if it touches the target's bounding circle. This was pretty inconsistent.
We changed it so that it will always use the target's bounding circle, but this means the potential reach of a skillshot is extended, and we have to slightly reduce the range of skillshots.
This explains why, for example if your dodging Lux's ultimate by moving upwards. You would still be hit by it even if you should have been out of it's range.
Also curious but, can you list what champions are effected by size changes and skill shots changed.