I get the feeling its more simple than this;
I believe some ancient shenenigans that occured before the shattering of Adonalsium (or during the shattering) laid the ground for some of the laws governing the interractions between Hoid and the Vessels. If that's the case, then there is ground for many loopholes we wouldn't even know about. To me that words with Wit's "UNLESS" epiphany, as his thought process goes there right after he feels Rayse is not acting as...well, Rayse.
So yeah, maybe there are some pre-existing deals between Hoid and the Vessel Rayse that are different then those involving Hoid and the Shard Odium, and that the former falling through influences the latter.