IMO this is politics, not economics, although to certain extent they are connected. Saudi's were apparently close to a very comprehensive deal package with the US before the recent escalation in the Middle East as they were close to brokering a Middle East peace. Some local and potentially regional players disrupted the peace at the late hour, potentially to derail the deal and undermine Saudi which is probably the dominant nation in the region by many measures and obviously undermine US influence.
To that extent, Saudi got nothing for the effort, while perhaps they think they should have gotten at least something. This could be a back-door to getting some of it, rather than really trying to get a mountains of Yuans that still have limited use. I am pretty neutral, so just putting the pieces of the puzzle together best I can. They don't match perfectly as they were not meant to.
Yuan is possibly the only credible BRICS currency. The risk levels associated with other BRICs currencies are very high. If the entire block backs Yuan, that could mean something on a global scale, but given the countries involved it might be difficult to impossible to get there. Them bartering in their own currencies will be interesting experiment, but sooner or later some of them will get burned.