Stopping at al-Abtah is not a sunnah. The Messenger of Allah ﷺ only stopped there because it made his departure easier when he left.
نزول الأبطح ليس بسنة، إنما نزله رسول الله ﷺ لأنه كان أسمح لخروجه إذا خرج.
Bukhari related it in the Hajj chapter (1765), and Muslim in the Hajj chapter (1311), both from the hadith of Hisham bin Urwa, from his father, from Ayesha, and I have mentioned it, with the wording being Muslim's. Bukhari's wording does not include, "Camping at Abtah is not a sunnah."