This is absolutely an issue. It has nothing to do with factory reset or your Roku login.
Once the Hulu channel (yes with a separate subscription) is added to Roku and logged in. There is no screen that lets you log out or unlink it unless you have the pin for a profile on the linked account.
Factory reset doesn't work. Deleting the channel and restarting Roku doesn't work. There is literally no way that I have been able to figure out to do it.
The Hulu app is horribly designed because there is no way to log out from Roku without being in a profile and Roku is horribly designed because there is no way to unlink Hulu and for some reason even factory reset doesn't work (Hulu keeping data on the system?).
When you add the channel all you see are available profiles. There is no way to click into a profile or elsewhere without a pin.
So no Hulu profile pin. Good luck.