Basically older iPhones without the modern secure enclave enforced the password attempt lockout period in software so the FBI obtained a court order to force apple to create and sign a new version of iOS that would not enforce the lockout period, which would allow the FBI to guess the password. Apple refused to create this new version of iOS and the FBI eventually retracted their request.
Modern iPhones enforce the lockout period in the secure enclave hardware so this is no longer something Apple could even possibly assist with.
https://en.wikipedia.org/wiki/Apple%E2%80%93FBI_encryption_d...