He literally answered your question in the very post you quoted, and I had answered it before that and so had others. To help it make sense, there are really only five very basic and simple concepts you need to understand which have already been explained but I've broken down for you below in the simplest terms possible and in a new format that might make it click better.
1. FargoRate doesn't measure the amount you run out, the quality of your stroke, how straight you shoot, which ghost you can beat, or anything of the like. FargoRate rates you by the only thing that matters when it comes to judging how good somebody is, which is how much you win or lose, against who, and by how much (and it takes your opponent's skill level into consideration so it knows just how impressive each of your win or loss amounts were and adjusts your rating accordingly).
2. Your opponent is always playing on the exact same easier or harder table as you are and the table is not somehow magically easier or harder just for you but not for him.
3. By looking at tons and tons and tons of matches for tons and tons and tons of players, including all the many player "exceptions" people were sure they had found, Mike has confirmed that the very clear trend is that people win at about the same rate against the same people/levels of players regardless of the table size (and regardless of how intuitive that may sound to somebody). Many people would have guessed otherwise but the actual win/loss performance data doesn't lie and he has over 19 million games of heads up play data on almost a quarter million players.
4. People often don't play to their normal potential on equipment they aren't yet used to, but it doesn't take all that long before this effect largely goes away as they get used to it. An analogy that might make sense to you is that when a fighter pilot gets assigned to start flying a different fighter, he isn't going to be quite as good in it in his first flight as he will be a few weeks later because at first he isn't yet used to the unique characteristics of the new equipment. It doesn't take all that long before he is back to performing at his typical level though, and he didn't magically have crappy piloting skills during this time, he just wasn't yet used to the unique characteristics of the new equipment yet until he learned them and adjusted for them.
5. There are people who, because of abnormally weak or strong particular parts of their game for their level (maybe they shoot straighter than Jayson Shaw but the rest of their game is Fargo 500 level), are a little more likely to win/lose based on the table size, but it isn't typical and the effects to the win/loss rate are still fairly negligible typically and more likely translates to a few Fargo points difference than dozens of points difference.