The documentation talks about nodes, so it seems that there is no way to get an ordered snapshot with strings...

If this could help, from previous running C++ code dealing directly with the XPCom layer, we found that, while using the ANY_TYPE:

• The resulting elements have always been returned (as expected) in the document order (aka a depth first tree walk).
• Even if not predictable at the query time, the exact result type, is driven by the expression query elements (btw, it would be nice to have it returned, to prevent recomputing it from query analysis).