I've been mulling this around for a bit. For context: I've owned timeshares for about 15 years, currently own five weeks, and have used both RCI and II plus one of the smaller exchanges (Grand Pacific Exchange).
the idea that they bought back a lot of SSR, OKW and AKL so they’d have inventory (from their own points) to deposit to II shortly after January 1 is intriguing. [...] I’ve read that DVC inventory appeared in RCI shortly after DVC switched from II, so that inventory had to come from somewhere.
I suspect DVC matters more to II than II does to DVC. It seems very likely to me that this was a matter of (a) the RCI affiliation was up for renewal, (b) DVCMC negotiated with both RCI and II, and (c) II offered them a better deal.
I was around for the II to RCI switch, and a member of both exchanges. I don't think it was that a lot of inventory got deposited as much as there just weren't many ongoing searches placed at the very beginning, so everything that got deposited ended up in the spacebank. Only the serious timeshare wonks (guilty as charged) knew the change was even happening for a good long while, so the pickings were easy right in the beginning. The same is likely to be true in II, for the same reasons.
It is also possible that DVC will prime the pump a bit, but they will do that speculatively with "regular" inventory. While there is expected to be a balance of inbound and outbound time, most timeshare systems that control (at least some) deposits have a good idea of how much will be deposited, what isn't in demand internally, etc. and will plan ahead rather than get caught at the end of a contract period holding a big imbalance.
touting to members that RCI had the better program with far more places to exchange into than II.
RCI, as a system, is larger and has more destinations and more inventory. II, as a system, has nicer resorts on average. However, there is an important caveat to that:
Looked at Interval’s properties, and they do seem a bit less mediocre than RCI’s.
They are, but most of the higher-quality ones have an internal preference period. For example, most inventory in a Marriott-affiliated resort (Marriott, Vistana Starwood, etc.) that is deposited has an exclusive period for several weeks during which time only other Marriott-preferenced owners can exchange in. In practice, that means the higher-demand Marriott inventory (the nicer Hawaii resorts, summer beachfront Hilton Head, ski-season Park City, etc. etc. etc.) is completely gone by the time non-Marriott exchange requests are considered.
Will DVC requests be given equivalent preference? I think it is unlikely---if memory serves, they didn't the last go-round). If DVC doesn't have access to inventory under preference it significantly limits the upside of this change for Members.
I’m always curious how this works, does the partner (RCI, II) only get points at DVC resorts when a DVC owner wants to trade into their network and vice versa? Or do they each hold a pool of points for each other and add/take as members trade in and out?
There are two ways this can work. One way: the outbound and inbound guests are "balanced." The points relinquished by Members depositing to the exchange company are backed by inventory secured by those points. Every resort that participates in exchange does this to some degree.
There is an (optional) second way: resort developers can deposit developer-owned inventory in order to generate traffic for sales tours from the guests who arrive. Vidanta (a developer of high-end Mexico resorts) is perhaps the most extreme example, but others do this too. Disney by all accounts
does not do this. They are easily able to rent out most of the inventory they own, and they spend next to no time trying to convince exchange guests to tour---at least, not beyond what they just do for everyone.
I have heard a lot of RCI members talk about getting DVC reservations and not a lot of DVC members talk about getting RCI reservations
That's probably selection bias. If you are reading Disney boards, you are reading about people primarily staying at Disney.