If Hajj is described as occurring during “well-known months,” then why is the Hajj season performed on…

Answer

In the name of Allah, the mentioned verse refers to both Hajj and the ʿUmrah whether performed independently or as part of the tamattuʿ rite. Although the days of Hajj are distinct from those of ʿUmrah, they are specifically defined from the noon of Arafah Day until the end of the nights spent in Mina. Allah is the Guide and He knows best.