OData Version 4.01. Part 1: Protocol/Section 14.3.1/7th Paragraph states

Key and other properties marked as read-only in metadata (including computed properties), […] , can be omitted from the request. If the request contains a value for one of these properties, the service MUST ignore that value when applying the update.

OData core vocabulary / UpdateRestrictionsType/ NonUpdatableProperties states

These structural properties cannot be specified on update
These two statements contradict each other. The vocabulary term description should reflect that what section 14.3.1 describes.