Routes feed "stop ETA updated" never fires

Hello our integration relies heavily on the routes feed to get real time updates, especially with regards to ETA. However, when we built our implementation ~1 year ago, we noticed the feed does not fire if the ETA changed, forcing us to long poll route ids when we knew a route was en route.

Upon reviewing the latest documentation, the possible values for the operation field contains stop ETA updated. That sounds perfect!

However, after analyzing our /fleet/routes/audit-logs/feed requests over the last couple of weeks (hat tip for the new Developer Metrics export), I never see stop ETA updated returned.