As a longtime Garmin user I have multiple devices as I am sure like many others. As a result I tend to choose the activity specific to the sport to serve my data needs at that time. My Edge 520 is the primary unit for cycling and syncs to Connect, Strava etc. From what I can tell on the Fenix 5 after a few activities - run tracked and synced via Fenix and a ride tracked on the 520, the last ride function isn't able to see the cloud data. This seems like a pretty basic thing since the watch connects and syncs all the time to my phone where Connect is actively managing everything. I presume this also means that things like VO2 Max from cycling data vs the watch will also not make it to the Fenix?
I can't imagine I'm the first person to notice this or perceive it to be possible to have the watch better reflect a fuller view. There are many years worth of data synced to Connect.