As W. Labov has passed away, I came across a comment reposting this screenshotted request, along with the paper in question:
https://betsysneller.github.io/pdfs/Labov1966-Rabbit.pdf
The paper is quite a rollercoaster, ranging from describing of disturbingly racist ideas about native Hawaiian and Black children that some scientists still pushed at the time (1970!*), to Labov's own disarmingly cute and humane solution to the issue of testing children's language abilities.
Edit: *1970 - according to the article itself, which is apparently based on Labov's 1970 talk; however, the URL suggests that the article was published in 1966, which is contradictory. I'll try to find out where and when this was actually published...
Edit 2: It looks like it is from 1970, from Working Papers in Communication, vol. 1 (Honolulu: Pacific Speech Association). It is surprising that a recently published book also claims that it's from 1966, probably the authors got the file from the same URL with the wrong year.
Edit 3: The original Twitter thread: https://xcancel.com/betsysneller/status/1516848959284678656
Something i've concluded about myself (i have autism) is that my ability to communicate pretty much perfectly reflects the ability of the person i'm trying to communicate with.
If they're good at talking then i'm fairly easy to talk to, but if they mumble or don't know the language well then it's basically impossible, especially if they don't take the initiative at all.