I remember at the time, it came out that the intruder had to have been exaggerating when he made that claim in his statement to the police.
McCollough's apartment complex has breezeway landings, with either two or four apartment doors on each landing. And the door of McCollough's apartment was only like 12' or 15' from the head of the stairway leading down. That's the staircase the intruder fell down after being struck by McCollough.
Now you probably read "thirty feet" from the intruder's police statement and thought, "wow, 30 feet, that's 10 whole yards, that's forever away from the home." But it was less than half that. Less than the length of one side of a professional boxing ring.
Heck yes, McCollough could still have been 100% in self-defense mode.
And you seem to have gotten stuck with just one side of the story.
p.s. McCollough's guilty plea shouldn't necessarily be read as an admission of any specific detail. Not a single one. Not even that he hit the guy. Instead, think of it as McCollough admitting that he wants this over with, before his final school year begins, without jail time, and is willing to enter a guilty plea under those conditions.