The webhook support make the sync react to changes faster, but the plugin will work 100% without it. We will do a full sync every 6 hours and capture any new patrons, as well as remove access for patrons who are gone. So you don’t have to worry about stuff like that.
For what’s worth it, this plugin was 100% created by us at Discourse without support from Patreon, so we are able to keep it working as long as their API exists.