"there'd be no license transfer of any sort, which means that any purchases made on Stadia would effectively be nullified as the service closes down." It lasted less than three years and will leave players with nothing to show. This is what people were predicting when Stadia lauched and part of the reason why it had poor adoption.
It is highly unethical to take away copies of the game that players had to pay full price for. Stadia owes them a retail copy of the games they purchased.
Adoption of stadia was sufficiently small that Google will pay the full refund cost just to prevent PR damage or lawsuit losses (and take the loss themselves, because the game developer isn't going to want to give a refund).