List<AbstractBounds> ranges = getRestrictedRanges(new Bounds(leftToken, p.getMinimumToken()));
when called with empty start key this means we have a Bounds(minToken, minToken), which hits the getRR special case
if (queryRange instanceof Bounds && queryRange.left.equals(queryRange.right))
logger.debug("restricted single token match for query " + queryRange);
Looks like this broke as a side effect of
CASSANDRA-1442. Prior to that a bounds from [T, minToken] was considered "up to infinity" by getRR so would span multiple nodes.