One of the avenues of debating Medieval Source regarding the primacy of various people in Transylvania is by introducing the hypothetical people of Bulaqs in the picture unjustifiable.
The Bulaq people were of a Turkic extraction. A very minor tribe who lived in modern day Tadjikistan in the mid centuries of the first millennium of the current era.
One of the written sources that is supposed to prove their existence in South Eastern Europe as late as the 13th century is a brief note written down in the The journey of William of Rubruck.
There are a few manuscripts available recording that journey, the earliest of which can be found at Corpus Christi, Cambridge, MS 181, pp. 321–398.
The snapshot below is from the digitized manuscript at page 345. Highlighting the interesting part of the text.
To support the idea that the ancient source mean Bulaqs by naming the Illac and the Blac in the text, the highlighted text is supposed to read as follows:
'Et qui sunt vltra Danubium prope Constantinopolis, et iuxta Pascatir sunt Ilac, quod idem est quod Blac : sed B. nesciunt Tartari sonare : a quibus venerunt illi qui sunt in terra Assani'
But on closer look the phrase has nothing about the Pascatur as a country name but rather a large pastures such as the Eurasian steppe up to which those Illac and Blac lived North of lower Danube. The Latin word is well used in the text many times pascat / Terra pascatur. We also have it in English as 'Pasture' or a Steppe.
Simple put, the reference is about the region of the Northern side of the Lower Danube where the Vlach (spelled 'Blac' in the text, to match their country name 'Blakia') lived at the time of Rubruck's voyages between 1253–1255 AD. They were shepherds as who gazed their flocks as we know it from various other Byzantine and other contemporary sources.
It seems to me that I am not the only one who have assigned that note to the Vlachs but also Raymond Beazley who provided a translation to the text and published it a while ago. One can find that online at Navigations.
One can see the note about the Valachians next to the phrase translated to English in the snapshot above.