It depends, but if you check in in two completely separate properties (read: not two sharing the same back-office) there is a good chance (read: not a guarantee) that you will receive a credit of two nights. You don't even need to sleep at either property (AFAIK you need to be present at check in, what you do after that is completely up to you and you can usually check out using the app so there's no need to be present either). I have no idea what would happen if the rewards account is audited.