> the computer who goes first won more than 56 percent of games, suggesting that there is a notable advantage to playing the first hand [...] There’s no way to know for sure what specifically causes this advantage, but perhaps giving one player initial control of the board has some beneficial effect.
"What specifically causes this advantage" is, to put it briefly, playing first. The first player will have about 0.5 more opportunities to score. In fact, since it's legal to pass, it's a trivial game theory result that any advantage in Scrabble belongs to the first player.
Consider what happens if neither player wants to go first. P1 passes. P2 passes. Now p1 has to play or the game is drawn. If the game is played with win3 draw1 lose0 rules, then p1 should play even if at a slight disadvantage. A 49 % chance of payoff 3 is better than a 100% chance of payoff 1.
I used to have a scrabble bot playing itself three times a day, posting its games to tumblr: https://scrabblebot.tumblr.com/
IIRC simulating an AI-AI game only took a short period of time (maybe a few seconds to a minute), so replicating the study with this scrabblebot wouldn't be too difficult.
"What specifically causes this advantage" is, to put it briefly, playing first. The first player will have about 0.5 more opportunities to score. In fact, since it's legal to pass, it's a trivial game theory result that any advantage in Scrabble belongs to the first player.