That's correct. The reference implementation of Bitcoin called "bitcoin core" doesn't support mnemonic algorithms so if you want to use your BIP39 mnemonic in it you'll have to derive the extended private key (xprv) from that seed phrase and then import that into core using "getdescriptorinfo" command with the desired derivation path.
Some people may hate me after I say this, but Bitcoin Core isn't a very newbie-friendly bitcoin wallet. BIP39 has been around for a decade, and they could have added support for it. The developers either don't want to, don't see a great need for it, or there aren't enough requests to add it. Sure, you can use the master private key instead, but it's even easier with a seed. Bitcoin Core's biggest plus is the full-node feature and being able to use a locally verified copy of the blockchain. Bitcoin Core as a wallet is of secondary importance and isn't for everyone.