ORA-FO-AGGREGATE 15.3 Aggregate Functions

*Functions and Operators, Section 15.3 Aggregate Functions*

"Except for fn:count, the sequence must consist of values of a single 
type or one if its subtypes, or they must be numeric."

But one example xquery in the xquery spec (4.10 Function Definitions) 
passes in a sequence of nodes to sum()

Which is correct: FandO or XQuery?