While this sounds impressive, I'll believe it when AlphaZero wins TCEC.
A nefarious suggestion would be that setting 1GB limit ensures that Alpha would always have the edge in depth as Stockfish would be forced to prune long lines to preserve hash memory.
Maybe someone who has read Stockfish source code can comment how Stockfish prunes hash memory.
The interesting thing is TCEC assumes a bit about the structure of the chess program. That is, the TCEC win-adjudication rule says that if both programs agree that one program is 6.5 pawns ahead for 8 turns in a row, they judge that program to be the winner.
But programs like Alpha don't have an evaluation function that operates in conventional units (like centipawns).
> We also measured the head-to-head performance of AlphaZero against each baseline player. Settings were chosen to correspond with computer chess tournament conditions: each player was allowed 1 minute per move, resignation was enabled for all players (-900 centipawns for 10 consecutive moves for Stockfish and Elmo, 5% winrate for AlphaZero). Pondering was disabled for all players.