Inconsistency in trip update example vs. reference documentation?

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The trip update examples maintained at https://github.com/google/transit/blob/master/gtfs-realtime/spec/en/examples/trip-updates-full.asciipb and shown at https://gtfs.org/realtime/feed-examples/trip-updates/ contain StopTimeUpdate messages with just a stop sequence number in the second and third entities.

Extract taken from the second entity:
> stop_time_update {
> # selected by stop_sequence. It will update the vehicle's arrival time
> stop_sequence: 10
> # with the default delay of 0 (on time) and propagate this update
> # for the rest of the vehicle's stops.
> }

The reference documentation for a StopTimeUpdate message however states that the _arrival_ and _departure_ fields are conditionally required, with the following clause:

> If schedule_relationship is empty or SCHEDULED, either arrival or departure must be provided within a StopTimeUpdate - both fields cannot be empty. arrival and departure may both be empty when schedule_relationship is SKIPPED. If schedule_relationship is NO_DATA, arrival and departure must be empty.

This suggests the example should specify at least one of the fields, or explicitly set schedule_relationship to _NO_DATA_. In my understanding, using _NO_DATA_ will effectively reset the delays to zero and stop propagation of any previously specified delay. _NO_DATA_ is however defined as "no realtime timing information available"—which may not be semantically correct when we know the actual delay to be zero.

What are your thoughts?