You can make one reservation under every owner name on your account for the same or overlapping dates and it doesn't matter if they are all at the same resort or several different resorts. Any reservations over that you have 48 hours to add a guest to the reservation or it will be cancelled and your points lost. It doesn't matter if you have used ARP for the reservation.
The purpose of this change is to stop the mega renters and point managers from booking up such a huge amount of the prime season inventory at the most popular resorts. Renting has grown at a phenomenal rate in the past few years often making it difficult for even the owners at those resorts to get reservations. Many of them have been complaining because they bought specifically at those resorts to be able to go to them and it really is kind of ridiculous that they have to be on the phone at 7am 13 months out to be able to get reservations. Some people don't even know if their requests for vacation time have been approved at 13 months out. Another problem is owners who hoard multiple reservations. Some do it to get multiple units using the cancel, rebook, upgrade process. Some do it because they allow their extended families and friends to use the owner as their own personal concierge. They are not used to having to get their act together to commit and the owner caters to them.
I can sympathize with the family/friend thing because a couple of years ago I put in a great deal of work looking for reservations at resorts in several locations that a family member thought they might like to go to with somewhat loose dates. And of course they wanted pictures and information on all those places to help them choose. All I was asking them to cover was $99 for the guest certificate fee if I ran out of free ones by the time of their stay. I had a lot of points tied up and after several weeks of waiting to hear back from them I gave them a deadline to choose something. They either couldn't decide or couldn't commit and I ended up with a lot of cancelled points. About two months later I see pictures on Facebook of them at a hotel in one of the towns on their list. The next time we saw them comments were made about how they found something on their own as they just didn't know if the accommodations I found for them were "good". So they paid something like $200 a night for a hotel room instead of having a two bedroom condo. My husband was livid and told me to never make another offer for them to use our timeshare again. His family by the way.
If you look at the really popular resorts there is absolutely nothing available for months but when it gets down to the 15 day window all those unsold or unwanted reservations are cancelled. The other owners who would have liked to be able to get those reservations are unable to go at such short notice. Within the 14 day window many owners who rent cancel reservations before the website closes at night and grab them back in the morning in the hopes of selling them. I had it pointed out to me what a problem it has become for the resorts in trying to assign units, keeping people in the same unit, staffing, cleaning the units, etc. With the these changes if you want to book more than one unit in the 14 day window before check in you must add the guest information at the time the reservation is made.
We may not like all of the coming changes but it isn't hard to understand why they were needed. And we can hope that they will benefit the owners they were intended to help.