Ven. Huifeng or Jeff may know.
The source would depend on which is the older sutra between the Avatamsaka & the Original Karmas one. Also, chapters can be and were, stand-alone sutras, so the earliest appearance of these stages is not known by me.
One should refrain from biased judgments and doubting in fathoming the Buddha and the Dharma of the Buddhas. Even though a dharma may be extremely difficult to believe, one should nonetheless maintain faith in it. Nagarjuna