Ah, wait so free users can keep syncing with Strava!? I totally misread your opening post then: “Future new users and current free users will be able download from Strava for a few weeks after which time a subscription will be required.”
reads very different than: “and free users can manually use the “Download old data” button to do the same.” which seems to imply it will stay, but just becomes manual.
If I’m reading it wrong, you can assume others are too (since I got here because other people linked it while saying you can’t sync with strava anymore unless you go intervals premium). You might want to consider changing your Opening post 
.