They are separate keys on you Humble redemption page. Ultimate is FE with all the DLC included.
Note that, if like me, you already own FE and just wanted Ultimate for the DLC, the Humble keys page will show Ultimate as “already owned” on Steam. You’ll need to click the Gift link as if you were going to send the key to someone else, then redeem the key by copying and pasting into Steam to actually activate all the DLC. It works, it’s just confusing.