As you say, section 1.18 of the spec says

> EL functions are mapped, resolved and bound at parse time. It is the responsibility
of the FunctionMapper class to provide the mapping of namespace-qualified
functions to static methods of specific classes when expressions are created. If no
FunctionMapper is provided (by passing in null), functions are disabled.

Also the javadocs contain _FunctionMapper_. I would assume that is still the way to go.