Well. That is different issue.
"Forgetting" simply means that if the page is in Google's archives (and hence will be retried), the 301 will fairly quickly make them forget the old URL. The new page will be archived instead.
If GoogleBot during its scans of other sites keep finding links to the old page, it will be obviously be revived again as an "interesting object to check out" so to speak. But because of the redirect, the new page stays the one indexed.
What did you think it meant that Google would "forget" the old URI? That they in addition to dropping the old URI from index and indexing your new page instead would also implement some sort of firewall list of dead URIs to remind themselves never to check that path, if someone else tells them about it once again? That is likely too much to expect. :)
Plus, they don't know up front. You could have revived it yourself. They'll have to check. Even if you 410/404 the old pages, GoogleBot would still come back to check them, but instead hitting errors.
The only way to fix the "revivals", I think, is to ask the linking sites to change their links so GoogleBot can stop finding the old links over and over.