Are the Xer'sai from the Void or are they Void-corrupted Sand Swimmers?

In the recent map reveal, one of the Shurima details was that people get around by riding on Sand Swimmers, which look an awful lot like Rek'sai. It's also been shown in the case of Kai'sa that people are not against slapping an apostrophe in a name when something gets Void-y, so Xer'sai might have been something different before Void corruption. It would also make sense for Xer'sai to be a species of Void-corrupted animals since no other Void creature has been shown to be a part of a species, the closest thing to that being Malzahar's Voidlings.