I saw that already when askod quoted it, but I don't find it credible. (The source, not the notion that the British colonial empire would condone such acts.) To be precise: it is a more or less detailed source on the much more gruesome slaughter in 1857 but a (secondary) source severely lacking in details on the late-18th-century thumbs-chopping claim, and I don't trust it on a correct paraphrasing of what it found in the original sources. This is because at the end of the first paragraph, it is conflating the East India Company's late 18th century monopoly enforcement for the selling of textile at a profit with the elimination of India's native weaving industry in the 1810s-1830s (which changed the equation for the Company, too). Thus, the lacking detail and inconsistency of the text throws up several questions and regarding possible (mis)interpretations:

• What kind of archives did Open access in that library? Contemporary sources like the Surat Factory Diary or official letters, 100 year old books, 20 year old books? Or did it access any sources at all? (Similar claims are in the two years older The Telegraph - Calcutta article also quoted by askod, but without any sourcing.)
  
• If Open didn't misread a source with a claim identical to William Bolts's, who were "the British" who were claimed to have chopped off fingers: soldiers, East India Company British agents, the Company's native agents, or local soldiers doing the dirty work? (Hand-chopping wasn't unheard of in Indian kingdoms, nor 'cooperation' with the British in the exploitation of the underclass.)
  
• What was the reason for the claimed chopping according to the original source?
  
• Were the 20 families who fled to the Nawab of Oudh specifically known to have fled after their thumbs were chopped, or before their thumbs were to be chopped, or have they just fled the Company's general oppression of weavers?
  
• Do sources say that the reason for the killings was the persecution that happened to the killers' grandfathers and great-grandfathers, or is that the Open author's speculation? (The more detailed account in the linked article says nothing on motives; the Calcutta Telegraph article claims that the weavers settled in that village in the 1830s only; and a 2010 article in the Telegraph - India references an unspecified early 19th century British crackdown.)

_{*Lunatic*, n.
One whose delusions are out of fashion.}