That would require some radically inconsistent thinking on their part. DM does occasionally release source code and trained models for other things, and the arms race logic (https://www.fhi.ox.ac.uk/wp-content/uploads/Racing-to-the-pr...) would even more strongly argue for not releasing anything, even research (they're privately owned, they don't have to publish squat), and especially not running stunts like the AlphaGo tournament which cost millions of dollars in order to terrify and impress competitors and heat up the arms race.

A more parsimonious explanation is simply that it's great PR to maintain rigid control over the family jewels and dribble out occasional sample games and bits and pieces while pretending to be generous. (No one has ever accused Hassabis of being bad at PR or not knowing how to milk the media.)