Editing the legacy.json file no longer works.
I decoded the file using that web tool (using the file version not copy/paste) and then encoded it without making any changes. The file is identical, and I replaced the original with this new one. That works just fine, and "access legacy" shows up on the main menu.
Then I made a small change (congruencePoints: 0 to congruencePoints: 50) I used vi to edit the file. I re-encoded it and put it in place. Launching the game overwrites the file with a default one, and 'access legacy' is no longer shown.
I expect the security field as the end is now more than just a UID, it's acting as a checksum also.