Tried that; now I get an error message on Garmin Connect: “Oops! Something went wrong loading your courses”. No idea what that’s about.
I am using the latest versions of GC and ER on iOS. Latest version of ER doesn’t behave exactly as described in the write up: there is no explicit ‘export’ function, only the standard share with (square with arrow) icon which gives 6 options including GPX, which is only option that brings up the copy to Connect button, pressing that brings up the error message.
I am not really surprised it doesn’t work. GC is a rubbish app and every time Garmin update it (about once a month), something else is broken.
Addendum; I don’t really like the Garmin Connect app and really only use it to upload rides from my Edge 810. But having played with it today following this thread, I found that Garmin have snuck in a route planner into the app, something that was missing for a long time. It’s a bit basic but it’s possible to plan a route on it, and then transfer to the GPS. Like EasyRoute, you need to have internet access to see maps.