So, he acquired some expertise or got very lucky on one day...
I would argue he was STILL a "lousy shot".
He missed his target 2 times out of 3.
But that's nothing.
In the movie "JFK", Kevin Costner (as Jim Garrison) has three teams of assassins - the most skilled marksmen in the world hired by the CIA - firing SIX shots and MISSING FIVE, which means if you apply logic to the movie, Oswald (33 1/3%) as a bad shot ("wudn't any good" as Walter Matthau said) was more than twice as accurate as three of the most skilled shooters in the world (16 1/2%).

