I dont think he wants to play alphago again. Go is a game that relies a lot on confidence: professional players almost never play amateur players casually, for example. Thats because if they lose to an amateur player, it will affect their mindset, their confidence, and they could then perform worse in the real professional tournament.
An argentinian amateur beat 2 strong professionals back then in 2001 in a major professional tournament: it was a huge sensation. Those two professionals basically disappeared from high ranking tournaments forever. It was said that the setback was so severe it affected them permanently(purely hearsay).
Its not good for a professional to play a game he thinks he will lose.