Consider the following mantra from Purusha Sukta 10.90.9
From that great general sacrifice Ṛcas and Sāma-hymns were born:
Therefrom were spells and charms produced; the Yajus had its birth
Atharava Veda as a veda is made up of Ricks mantras only.
According to Rig Veda Anukramanika, the composer of this hymn is nArAyana, but not Vyasa.
Tenth Mandala is supposed to be latest one. However, even this hymn did not mention Vyasa to be compiler of Vedas.
Ramayana, which preceded Mahabharata, contains reference to 3 Vedas only. Sri Raama says Sri Hanuman is well versed in 3 Vedas only.
न अन् ऋग्वेद विनीतस्य न अ--यजुर्वेद धारिणः | न अ--साम वेद विदुषः
शक्यम् एवम् विभाषितुम् || ४-३-२८
"Nay...the non-knower of Rig Veda, or the non-rememberer of Yajur
Veda, or the non-scholar of Saama Veda... can possibly, or truly speak
There was a reference to Atharvasirsha in 15th Sarga of Bala Kanda.
इष्टिं तेऽहं करिष्यामि पुत्रीयां पुत्रकारणात् | अथर्वशिरसि
प्रोक्तैर्मन्त्रैः सिद्धां विधानतः || १-१५-२
"I will procedurally conduct the ritual contained in the preamble of
atharvasirsha with procedural hymns, called <>putra kaameSTi i.e.,
the ritual that bestows sons, for your benefit."
However, Sargas 15 to 17 are interpolated ones. Hence, this mention of Atharvasirsha in Ramayana also must be interpolated one.
Further, if Ramayana period was aware of Atharva Veda, apart from Rik, Yaju and Sama vedas, then Ramayana would have been called Panchama Veda, as Mahabharata used to be referred to as such, as Ramayana also contains many issues related to Dharma.
Further, division of Vedas was already done, as was evident from the words of Sri Rama as mentioned above.
Hence, division of Veda by the Sage Vyasa must be an interpolated story.