I don’t know anything about the site linked from the Wiki page. But would cycling.waymarkedtrails.org serve your purpose? Clicking the “Route” button shows the details of all routes in the current map view with the option to download as GPX.
That should work for route relations, but is unlikely to work specifically for 1213626 as this is oddly tagged - it seems to be tagged as a boundary, not a route of any kind, and waymarkedtrails.org is designed for routes.
If you check the history of the route, you’ll notice that some newbie (probably by mistake) changed the tagging of the route yesterday. I’ll recommend asking him why.
As far as I know waymarkedtrails.org doesn’t attempt to order the elements of a relation so if the underlying data is not ordered by mappers this will affect the GPX and elevation profiles.