I noticed this before but if abhidhamma was “invented” by generations of monks after Buddha Gotama, I would expect it to contain many inconsistencies with the Suttas. But so far, I have not seen any significant contradiction.
Additionally, the so-called “scholars” who make those statements are non-ariyas who frequently make mistakes in their translations of the Pali Tipitaka. So I wouldn’t trust them. That being said, it has been stated that Abhidhamma in its final form was completed in the 4th Buddhist Council, almost 5 centuries after our Sammasambuddha. But the main framework was already there in the 1st council:
“21. Pañcasatikakkhandhaka” section of the “Cūḷavagga” of the Vinaya Piṭaka contains a small section at the end called Tassuddānaṁ which summarizes the events of the First Buddhist Council. It contains this verse: “Upāliṁ vinayaṁ pucchi, suttantānandapaṇḍitaṁ; Piṭakaṁ tīṇi saṅgītiṁ,akaṁsu jinasāvakā.”
- That says: “Venerable Upāli recited the Vinaya (Upāliṁ vinayaṁ pucchi,) Ven. Ananda recited the Suttas (suttantānandapaṇḍitaṁor sutta ānanda paṇḍitaṁ), and all of the 500 Arahants present recited ALL THREE Piṭaka (Piṭakaṁ tīṇi saṅgītiṁ,akaṁsu jinasāvakā.)