From al-Malfudh Sharif, pg326:

Question
There are many places where the comment of the Imāms of Tafsīr are not accepted, e.g. Qādī Baydāwī and Khā’zin both have specified that Towrāt still has comprehensive details of everything.

Answer
Qādī Baydāwī and Imām Khā’zin rađiyAllāhu ánhuma are not Imāms of Tafsīr. To be an Imām of Tafsīr is one thing and to compile a book on the subject of Tafsīr is totally a different thing altogether. The Imāms of Tafsīr are the illustrious Sahāba rađiyAllāhu ánhum and only the distinguished ‘Ulamā amongst the Tāba’īn rađiyAllāhu ánhum. Not every Tāba’ī is an Imām of Tafsīr, only the most knowledgeable amongst them who have specialised in this field are regarded as Imams of Tafsīr. Imām Mujāhid rađiyAllāhu ánhu was certainly an Imām of Tafsīr and he perfected the field under the tutorship of Sayyid al-Mufassirīn Jabar al-‘Ummah, Sayyidunā ‘Abdullāh ibn Abbās rađiyAllāhu ánhu. His commentary will certainly be accepted as authentic and unquestionable.