I can't tell whether he is serious or is just trying to have a laugh at other people's expense.
At the start he gave the impression that he was going to explain why moving one speaker more to the front or to the rear would not make sense, and also why it does not matter if the wires aren't the same length, at least not from the perspective of time difference. Sound travels in air at 343 meters per second, and a typical difference in the distance to one speaker vs. the other is about a meter. It follows that a typical value for the time offset for the two speakers is on the order of 1/343 second, i.e., a few thousandths of a second. By comparison, the time offset that occurs due to the speaker wires having lengths that are different by the amount shown in the video is on the order of 1/10 of a nanosecond.
No one could possibly be as confused as he makes it seem that he is. He knows that what he is saying is nonsense, and is just trying to have a little fun, or something similar to having a little fun. At about the 2 minute mark he started going off the rails, especially when he said that you should never ever use speaker wire that is not the exact same length. At the start he made it seem that he was going to explain why the idea suggested by the question didn't make sense, but then he eventually turned it into jabberwocky.