When I was looking into this I also was thinking that since Sugimoto doesn't appear anywhere else, MAYBE McGraw was trying to pull a "Chief Tokohama" again.
Back in 1901 McGraw tried to pass off blackball star Charley Grant as an American Indian named
Chief Tokohama. McGraw discovered Grant in Hot Springs where many black ballplayers wintered, playing baseball for the various upscale hotels to amuse the guests. McGraw concocted the fake ID and signed Grant to a Baltimore Orioles contract. The reasoning was that an American Indians playing in the big leagues would not be that big of a deal as opposed to trying to re-integrate the game.
The ruse fell apart before the season started and Grant went on to have a nice long career with the Cuban X Giants and Philadelphia Giants.
Could Sugimoto have been another black ballplayer McGraw found playing in the Hot Springs Hotel League?