In ODATA-818 we added the ability to omit null or default values based on a preference request header. If this preference was specified in the preference-applied response header, the client could assume that any missing properties had the null/default value.

We had to call out certain cases in which nulls/defaults could not be omitted, such as delta and request payloads.

We did not specify, though, if a property has annotations, but default/null value, whether it could be omitted. Indeed, in many cases the annotation may be describing why the property was value was omitted, and restoring it to a null/default may violate the intention of annotating the value as being missing.