"...as I am." ought to be accepted as correct as it is grammatical correct in English.
Is not proper English "She is as beautiful as I" (like saying "she is as beautiful as I am")?
That depends on what people you are talking about. "As I" is certainly correct. I knew Duo would want "me" but it hurt my grammarian soul to give to him. (I probably wouldn't say, "As I," but I would say, "As I am" in conversation.)
The most respectable ESL materials (e.g. Oxford University Press) teach "as me" so I guess it has become standard. (BTW I put "as I am" and was marked wrong.)
They teach what people generally say but neither that nor Duolingo makes "as I" wrong. Add the understood verb and nobody says, "me am." The complaint is that Duo rejects a correct answer.