A quick search to WP Dog Intelligence [1] will quickly note that there have been cases of 1,000 words and this is actually fairly well known. It's perhaps interesting that researches are confirming anecdotal reports online, although as noted in another comment below, there are 10M+ videos from multiple channels all on the same subject. I donno, it's like humans are just realizing animals might not be that less intelligent. Parrots ask existential questions. Prior research on dog language:
"2008, Betsy, a Border Collie, knew over 345 words by the retrieval test, and she was also able to connect an object with a photographic image of the object, despite having seen neither before."
(mentioned in article) "Rico initially knew the labels of over 200 items [and] inferred the names of novel items by exclusion"
"2013, a Border Collie, "Chaser", who had learned the names and could associate by verbal command over 1,000 words[...], and [was] capable of linking nouns to verbs"
[1] https://en.wikipedia.org/wiki/Dog_intelligence#Learning_and_...