UMLR — Lifeline "same_classifier" constraint has an inconsistent specification

The English description of the "same_classifier" constraint is much more restrictive that the specified OCL expression (see 17.12.17.5):

The classifier containing the referenced ConnectableElement must be the same classifier, or an ancestor, of the classifier that contains the interaction enclosing this lifeline.

inv: represents.namespace->closure(namespace)->includes(interaction._'context')

Please clarify.