Agreed. If I try transferring the GPX to my laptop and manually uploading to Strava, it gives an error message. It seems the Flow app is missing some required details in the GPX.
I had the same error. Shouldn't have to export with a pc either eh. They should make this easy within the app like an auto sync to Strava.
Hopefully there are more improvements to come.
One of my favourite parts with the flow app is how it keeps track of how many miles you do in each mode.