Yes it is ambiguous, in my personal interpretation I do not see any mandatory call for the Spanish language. Just it is mentioned that it can be used.
For what I know, after the change in the operation manual , vueling was required by Aena to prove that all its pilots would then be able to speak Spanish.
so, is the level 4 or 5 need to be renewed every tot years? I mean also the Spanish one? At the time I did it they were not allowed to give more than 4.