The purpose of the suggested VPN was to send your traffic to FB from outside the EU. That would then make it so FB didn't prompt you with new EU TOS, so you could click through (since you wouldn't be governed by GDPR). But the catch is that the traffic outside the EU wouldn't be governed by GDPR there is also no recourse if they don't hard delete( of course it would be hard to verfiy if they did like you pointed out).