So if a wallet was created instead of imported you will be able only to restore whole wallet with seed and you cannot to extract for example private key for ETH.
Yes, as seed is much easy to remember than private keys. But if you want to get the specific private key of your wallet, you can get it using different tools, like
Mnemonic Code Converter by iancoleman. Or you can just import your seed to electrum, and export the private keys of the specific address using the wallet in the wallet tab