Il-nam’s “elimination” was perfectly timed
Gi-hun’s kindness ruined Il-nam’s original plan to leave, and the old man had to come up with a convincing “elimination” during the marbles game.
When we look back at episode 6, it’s apparent that he couldn’t have faked his death while there were so many people around. Therefore he stretched out the test as much as possible by walking the set searching for his house. From the end of that episode, we already knew that he wasn’t forgetful – everything was planned to a tee.