This is a better thread to post in, so yes, I am posting this a second time.
Because it annoys me that much.
This is false. It is not "effectively a one game lead." If San Antonio wins one more and Phoenix loses one more, the Spurs will still be 1 game behind the Suns.
I've heard this in the past in instances where it makes sense. An example would be if the Suns had a 2-1 season series lead, you might say they "effectively have a three game lead on the Spurs." Because the Spurs would need to be one game ahead of them to get the 2 seed.