It doesn't "Need" to be separate. The thing that matters is your worker: 'bc1....123' needs to be the address that signs the message OCEAN generates from your Lightning Bolt12 offer. The worker can be your on chain address for your Lightning node BUT you'd have to enter your seed phrase into electrum, or sparrow or some othe wallet software that can sign a message. Core Lightning doesn't have that functionality. After signing the message in that software you can paste it into Ocean's config page.