I tested a bit further, it's doing anything requested. But, to be fair, this is a lot where he is actually busy a lot of the time, so I'm unsure if my timing is unlucky or a bug at this point. He did cook one party meal all by himself.
I'm still confused on the sleep tho. If you send a butler to bed, do you need to wake them up too?
ETA: I just played a bit and he does the 'take money from being assigned cooking but not actually cook while otherwise idle' with the 'could not carry out requested task' notification. I can added a post to the bug report.