Ḥajjāj ibn Arṭāʾah is considered weak, and Allah knows best.

The report of Surāqah ibn Mālik ibn Juʿshum
Imām Aḥmad said: “Makki ibn Ibrāhīm narrated to us; Dāwūd—meaning Ibn Yazīd—narrated to us; I heard ʿAbd al-Malik al-Zarrād say, ‘I heard al-Nazzāl ibn Sabrah, the companion of ʿAlī, say: I heard Surāqah say: I heard the Messenger of Allah ﷺ declare, ‘ʿUmrah has been incorporated into Hajj until the Day of Resurrection.’ Surāqah added, ‘The Messenger of Allah ﷺ performed qirān during the Farewell Pilgrimage.’”

The report of Saʿd ibn Abī Waqqāṣ: that the Prophet ﷺ performed tamattuʿ—linking Hajj to ʿUmrah—which in reality is qirān
Imām Mālik related, on the authority of Ibn Shihāb, from Muḥammad ibn ʿAbd Allāh ibn Nawfal ibn al-Ḥārith ibn ʿAbd al-Muṭṭalib, that he said: He heard Saʿd ibn Abī Waqqāṣ and al-Ḍaḥḥāk ibn Qays, in the year Muʿāwiyah ibn Abī Sufyān performed Hajj, discussing the practice of performing ʿUmrah during the months of Hajj and then completing the Hajj (tamattuʿ). Al-Ḍaḥḥāk remarked, “Only someone ignorant of Allah’s command would do that.” Saʿd replied, “What a vile thing you have said, nephew!” Al-Ḍaḥḥāk retorted, “ʿUmar ibn al-Khaṭṭāb used to forbid it.” Saʿd answered, “The Messenger of Allah ﷺ did it, and we did it with him.”

Al-Tirmidhī and al-Nasāʾī both transmit this ḥadīth through Qutaybah from Mālik, and al-Tirmidhī declared it sound (ṣaḥīḥ).

Imām Aḥmad also said: “Yaḥyā ibn Saʿīd narrated to us; Sulaymān—meaning al-Taymī—narrated to us; Ghunaym narrated to me: I asked Ibn Abī Waqqāṣ about mutʿah, and he replied, ‘We practiced it, whereas this man is a denier of the Throne’—meaning Muʿāwiyah.” He reported it in this abbreviated form.

Muslim likewise included the narration in his Ṣaḥīḥ through the lines of transmission of Sufyān ibn Saʿīd al-Thawrī, Shuʿbah, and Marwān al-Fazārī.