With no explanation, label text_A→text_B with either "DON'T KNOW", "NO" or "YES".
text_A: Before the coming of major industry, Abertillery was little more than an area of scattered farms in the ancient parish of Aberystruth. In 1779 the parish minister Edmund Jones described the area thus: "The valley of Tyleri... is the most delightful. The trees... especially the beech trees, abounding about rivers great and small, the hedges and lanes make these places exceeding pleasant and the passing by them delightful and affecting... in these warm valleys, with the prospect of the grand high mountains about them would make very delightful habitations." In 1799 clergyman and historian Archdeacon William Coxe toured the area and in writing a diary of his travels described it as "... richly wooded, and highly cultivated...we looked down with delight upon numerous valleys... with romantic scenery". The entire population of Aberystruth parish at the turn of the 19th century was just a little over 800. It is well known what the population of Abertillery was in the very low hundreds at the time, but not all of them would have spoken Welsh only.
text_B: Are the best modern-day estimates of Abertillery's eighteenth-century population figures likely to have come about from contemporaneous conversations between English officials and bilingual town officials and/or educated residents?
YES.