I saw a video where Seirawan himself spoke about this, and he suggested a big motivation was to eliminate the Berlin defense (3.-Nf6 in the Ruy Lopez
This can lead to a position that tends to be more drawish than usual, which would be this position
).
The game hasn't been solved and the strong computer programs also loose to each other sometimes.
Anyway interesting post.
RE: S-Chess, The Best Chess