Hi!
I've come from Polar camp to Garmin a year ago. I find it difficult to times spent on different HR Zones in Garmin Connect.
Most obvious error I'd like to ask is could you check which sport profile HR Zones are used for Trainerroad imported workouts? It seem to use "general" zones, not bike. And even though one would switch sport time for such an activity, HR Zones are not updated.
My workflow is usually to record workout also on my FR945 to catch training load for Garmin, but I will later only leave Trainerroad workout on my log since it has all interval data etc.
Since Traineroad workout is imported as indoor bike workout, I believe issue is on Garmin Connect end. Please let me know if this should be addressed to Trainerroad instead.