Hmm… No, I’m not really saying that, I think both the Biles and Dos Santos II are sufficiently rare that there’s no reason making a claim about which is ‘objectively’ harder. The double back half-out vs. double arabian tucked is a different story, and yet I don’t think it would be sensible to rate a double back 1/2 twist any higher than a full-in despite its rarity (is it even in the code at all?), so E for both also fine.
In other words, when you have multiple valid reasons not to overcomplicate the internal logic of the difficulty ratings, then simply don’t – thus, defaulting to not distinguishing difficulty on the basis of when a twist takes place makes most sense to me. (and like I said, not in favor of putting arabian-style skills in the front tumbling category for that same reason).