It has no advantage whatsoever. Any resale members from Riviera cannot book into original 14. Any resale members from original 14 cannot book into Riviera. There are will be, in any given time period going forward, more resale buyers for the original 14, than resale buyers for Riviera. Thus a much smaller proportion will not be able to transfer into the original 14 than transfer out as time goes on. Also given Riviera is new, most buyers will not be selling for some time (average period of ownership 10-14 years). What this means is a comparatively modest number of Riviera owners locked out of your resort, whilst most can book your resort. Less people who own at original 14 can book into Riviera (all resale post Feb) so place more pressure on original 14.
So it actually makes your 7 month booking window worse.
It also doesn't help Riviera owners, who could (see below) eventually have a ton of resale being unable to book OKW and SSR fighting for the coveted 11 month booking window- with nowhere else to go.
The only people who will gain, very marginally as so few resale contracts are currently affected but this will increase in the next few years, is Riviera buyers who will for a short period, until their own resale contracts start to hit the market in higher numbers, have a slightly smaller proportion of original 14 being able to book their property.
Of course, they are going to see significantly depressed resale values and be hit hard in their pockets.
Anyone who thinks this was done for the good of the membership, needs to really think about this- they did this so they could squash resale, which if they manage it and manage to ROFR contracts back cheap and thus mainly recycle and sell direct, could actually help original Riviera owners with the problem of too many of their co-owners (resale) being locked in. That will however not help original 14.
This is a long term plan. Gradually as the original 14 get closed down and resold/ rebuilt with the new rules, resale will be well and truly squished.