How Did Yuta Copy Dhruvs Technique?

We know in order to use a copied CT Yuta needs Rika to devour a good portion of the original user.

But we never see Yuta call upon Rika to eat a part of Dhruv so how did he use his technique later against Uro?

Do you think Gege didn't include that because he didn't want to reveal how Yutas CT worked so early?