When setting up the kingdom I was not allowed to start the game when I had chosen Herb Gatherer as the card for Way of the Mouse. It said that the selected card is not a kingdom card. But it is a kingdom card. I guess that there's some code preventing it from being chosen at random, maybe because the "rotate" effect would do nothing, but there's no reason it couldn't be chosen by the user.
Apparently something was changed server side, this seems to affect all eligible split pile cards from Allies, though not from Empires. I'll forward this.