That said, a highly skilled and experienced player who knows their opponents' individual styles would do better than GnuBg against non-world class players. GnuBg is programmed to be most effective against world class players and doesn't know anything about exploiting the weaknesses of lesser mortals (ie. the vast majority of players on the planet).

For instance, some players are scared of the cube and will drop a cube that really ought to be taken. GnuBg cannot conceive of such an idea, let alone make that play, so it loses points that a canny human cubist would gain.

There is a rule of thumb in backgammon, "If in doubt, hit", which is applicable because hitting, even in what seems to be an amazingly risky situation, is often the best course of action. Sometimes such a hit requires knowing how to deal with the aftermath, be it favourable or not, but many times it doesn't take top expertise to come out better on average after a hit.

Yet there are situations where most people will hesitate and others where many will be cautious. More than that, there are players who, in some situations where a hit is clearly the best option, will still not do it, perhaps for fear of being hit in return. GnuBg (and every other bot that plays backgammon) knows nothing of opponents missing hits that they should make. It always assumes that the opponent will make the hit and so it doesn't leave a blot when being hit would lower its chances too much. A canny human player will sometimes leave provocative blots knowing that doing so improves their position and that the blot will probably not be hit.

Another advantage that human players have over GnuBg is that GnuBg always expects the opponent to cube when the time is right for it. There are so many players who are slow to cube or even don't cube at all and each missed cube means that a different move might have been more advantageous. The bots miss these and all sorts of other opportunities to play less than world-class moves yet win more points.

Yes, except for the risks outlined above that require understanding and recognising playing styles other than world-class perfect.