Thanatos wouldn't know about any myths about pomegranates either. He just knows that Zagreus eats them and uses them to strengthen his abilities.

"Still with the seeds and with the rind it's own thing, just... edible." The other option reminds him of the pumpkin cake the Red Team got as a "reward." It looked like one thing and tasted like another. "And if it could still look like a pomegranate... I don't know how that works."

Embarrassment is clearly on Thanatos's cheeks, flushing a little golden as he stumbles over his odd request.