The whole point for checkbox on N-400 was to update SSA with citizenship status without visiting SSA. It worked for a limited time, and many citizens used it successfully. There are reports on Visa Journey people receiving new SS cards and having status updated for them automatically. However, earlier this year, Enumeration Beyond Entry (EBE), the technology enabling this, was paused. So now everybody has go go to SSA regardless of what they check on N-400. It doesn't make sense checking "yes" and providing SSN on N-400 form anymore. Details in my thread mentioned above, there's a lot of materials going to specifics.