Go was considered to be difficult for computers because of the high branching factor compared to chess. DeepMind still beat the best humans there pretty comfortably, with similar amounts of training to what allowed it to compete with the best engines in chess and shogi.

I'd expect AlphaZero to hammer the best humans given a similar amount of training (~100,000 2017 TPU-hours) in this shogi variant, so no increased training time at all by that metric. Maybe a more meaningful metric is how closely it approaches perfect play, but we don't have a good way to measure that.