In the same sukta, there is

नाभ्या आसीदन्तरिक्षँ शीर्ष्णो द्यौः समवर्तत |

पद्भ्यां भूमिर्दिशः श्रोत्रात्तथा लोकाँऽकल्पयन् ||१३||

Does पद्भ्यां भूमिर्दिशः also have a hierarchical value connotation?

Body part descriptions are there in the Sukta in relation to many other cosmic entities too. Are they all hierarchically viewed? If no, then why this argument be limited only for the socirty aspect?

Though Vibhaktis are different for first three quarters and the fourth quarter, the meaning has to be taken consistently and uniformly for all the four quarters of the mantra. So in all the four quarters, it means that four varNas are depicted as forming equi-status components of an organic entity.

Hierarchy is not there in sAyaNabhAshya too.

It is quite natural for those with hierarchy in their attitude or those who enjoy wielding their superiority to misquote books or misinterpret them in the direction of their favor. 

But their misquotation or misinterpretation can not be the basis of the interpretation of the text. 

Particularly a historical study citing such a text  as the source or origin of hierarchy, depending on its wrong interpretation, loses its validity on account of the wrongness of the interpretation.