event.attributes.Track Duration availability appears to depend on the selected "Of Type" — is there a fixed mapping, and can we rely on it for all object types?

Observation

When creating/editing a Rule with:

• "When Event" = Analytics Object Detected
• "Occurs At" = a camera running CVEDIA-RT analytics
• "And Object" = Has attributes

...the event.attributes.Track Duration token is sometimes available in the "Do Action" → HTTP(S) Request → Content field autocomplete, and sometimes not, for the exact same camera.

After testing, we found this is tied to the "Of Type" selection (e.g. Person vs. other object types) — not to the camera or to caching, as we initially suspected. With some "Of Type" values selected, Track Duration appears in the attribute autocomplete; with others, it does not.

Questions

1. Is there a fixed, documented mapping between object type (Of Type) and which attributes (including Track Duration) that type's analytics publish? I.e. is it expected/by-design that some object types simply do not produce a Track Duration attribute at all?
2. If such a mapping exists, where is it documented — is there a reference listing which attributes are available per object type for the CVEDIA-RT engine?
3. Can we rely on Track Duration being available for every object type, or is it inherently type-dependent and we should not assume it's universal? We need a mechanism that reliably reports "how long has this specific object been continuously tracked" regardless of whether it's a person, vehicle, or other detected type.

Context

We're building an integration that needs to detect when any tracked object (of any type) has been continuously present in a camera's scene for a configurable duration threshold, and we want to know if event.attributes.Track Duration (via the Rule's HTTP Request action) is a reliable, type-independent source for this, or if we should instead rely on GET /rest/v4/analytics/objectTracks (which returns startTimeMs/endTimeMs per track uniformly regardless of objectTypeId).