Turns out "anyone can edit" also meant anyone could mess with the sharing settings. So I've made it read only, which is a pity. Will investigate alternative hosting arrangements that might support pull requests at some point...
Which is what stopped me from using them for some serious crowdsourced data projects in the past. This was a sheet I had lying around anyway and thought others might find useful :)
Might be nice to have someone define a clean 1:1 mapping between a google sheet/airtable and a git repo...