For Fine Hotels and Resorts (FHR), only a one-night stay is required to get the credits. You should get the credit for each night if you alternate reservations each night between the two of you. PMFR was probably thinking of The Hotel Collection, which requires a two-night stay to get the credits.

I have heard people having their spouse check in separately on the second night and moving rooms out of an abundance of caution to make sure that the hotel doesn't try to withhold the credits, but I've also heard of people asking the hotel to let them stay in the same room and the hotel accommodated them and gave all the benefits without any problems. I've never heard anyone say that they kept the same room and the hotel withheld benefits for the second night, but it might depend upon the hotel. The fine print only says that if one person stays two consecutive nights that it will be treated as one reservation for purposes of the benefit, so having a second person for night two should entitle you to benefits for night two.