Hey @M_R, thanks for reaching out to the Community!
Yes, that's correct.
Since you currently have a subscription involving Hulu, you won't be able to switch to Duo while your current bundle is active. In order to get Duo, you'll first need to cancel your current plan and resubscribe once you revert back to free. Keep in mind that the access to the Hulu bundle will then be lost and won't be able to add it back to your account. This also holds true when you're upgrading to Premium Family or any other plan.
There is some more information on Premium Duo here.
I hope this clears things up!
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