Is the emergence of the Mahdi from the East and the completion of his pledge of allegiance in Mecca considered a contradiction, and what are the Eastern lands intended?

Ibn Kathir mentioned that the Mahdi will emerge from the East and receive allegiance at the House [Kaaba]. The intended East is the eastern direction, starting from Najd of Iraq and beyond. There are weak narrations that specify this as Khorasan, such as the hadith, "Black banners will emerge from Khorasan, nothing will stop them until they are planted in Aelia (Jerusalem)." Khorasan includes parts of Afghanistan and Iran.