Posted 2014-April-08, 14:36
The book bid for this hand is 4♦. Since Lycier plays with basic bots, that's what he gets.
Advanced bots use simulations, and the bids it considers are Pass, 3♦, and 4♦. It usually chooses 3♦, because either this gets the same result as 4♦, or partner has a decent hand with spade stopper and bids 3NT. All the auctions that reached a successful 6♦ began with 3♦, because there was room for West to show strength in the side suits. West rarely bids over 4♦, because it's dangerous to keep bidding without a fit. (This is probably why many advanced players use Leaping Michaels -- using so much bidding space is not productive less well-defined hands.)
The rule for bidding 3NT doesn't allow 6 cards in any suit, but we perhaps could add a rule that allows a good 6-card minor like this. Although bidding 3NT is somewhat unilateral -- if 6♦ is possible, you'll never find it that way, since the bid would also be made with a strong, balanced hand.
BTW, in direct seat the robot doubles with this hand. It only bids diamonds when balancing.