Recently this changed, where if my opponent resigns it won't let me continue playing against a bot. This is really annoying because half the time I'm going to win they just quit, and I don't get the satisfaction of actually winning the round. Or when you start a game and it seems like a really cool set with great combos, then the opponent just never starts and it times out.
This new behaviour is not planned to change, unfortunately. What happened is that now you can only continue with bots if you have 'access' to alle the cards in the game. Having 'access' means they have to be part of your subscription.
So all-base games are fine, but a player without a subscription will in a game against a player with a subscription not be able to continue against bots, as the kingdom will (with almost certainty) contain non-base cards.