On a rare occasion I have gotten two credits but as a rule you can not get elite credits for rooms that you do not occupy. What usually happens is if I take my family with me and book more than one room, I get points for all of the rooms but elite credit for only the room that I am staying.
I haven't booked multiple rooms that often but,I've always gotten only a single night's credit when I did. peymanagement appears to be correct. I also get points for all of the rooms but elite credit for only the room in which I am staying.
I have done this a couple of times and found that you get one night, but points for everything you pay;
this is in accordance to the rule that elite nights (next to all the Marriott CC bonus nights; this CC is not available for me; grrrr!) are actual nights, stayed by the Rewards-account holder