According to what I understand one doesn’t necessarily need seed keys as long as you have the public and private spend and view keys. Am I correct? The seed keys just are an easier alternative. In the past I created keys with the Migration Wallet, but I don’t remember writing down seed keys, but I definitely got the other set of 4 keys (public & private spend key / public & private view key).
The mnemonic seed is just a word-based way of recreating the private spend key, and from there, all other keys and address are generated from the private spend key.
Keep the mnemonic seed and/or private spend key safe, as the priority. All the others can be reobtained from there.