Almost a year late in digesting the changes...

Relevant T&C:
==Members will only earn credit for each Qualifying Night which is part of a Stay at a Qualifying Rate, for the guest room the Member personally pays for and stays in, and not for any additional guest rooms.

Quite clear:
https://www.marriott.com/loyalty/terms/default.mi

2.1.d. Qualifying Stay. A “Stay" or “Qualifying Stay” means all consecutive nights a Member registers for, and personally pays and stays at any Participating Property, for which the room is billed to the Member.
i. A “Stay” is a stay of one or more consecutive nights at the same Participating Property by a Member who: (A) provides his/her Membership Number at the time of reservation or at check-in; (B) pays a Qualifying Rate or redeems a Points redemption Award or a promotional Award for the stay; and (C) stays in one of the reserved guest rooms. If a Member checks out of a guest room and then checks back in to a guest room at the same Participating Property within 24 hours, it will count as a single stay for purposes of calculating Stays and issuing Member benefits. A Member may only earn Points for up to three (3) guest rooms during any Stay if he/she stays in one of the reserved guest rooms and pays a Qualifying Rate or redeems a Points redemption Award or a promotional Award for all of the guest rooms.
ii. A “Qualifying Stay” is a credit pursuant to these Program Rules that counts toward earning Elite Night Credit. Except as otherwise set forth in these Program Rules, including in Section 7.1 and 7.2 below with respect to MVC Owners and Vistana Owners, Members will only earn credit for each Qualifying Night which is part of a Stay at a Qualifying Rate (as described in 2.1.e.), for the guest room the Member personally pays for and stays in, and not for any additional guest rooms. Members do not receive Elite Night Credit on stays at Non-Qualifying Rates (see 2.1.f.).
iii. Members cannot earn or receive benefits at multiple Participating Properties for the same stay date(s).
iv. Only one Member per guest room can earn Points/Miles and Elite Night Credit, as well as receive benefits. If there is more than one Member staying in the same guest room, the Members must decide upon check-in whose Membership Number will be applied to the guest room provided it is the same Member who will be paying the bill.