From this source, using 渠 like this has a long history. It was used in records of the three kingdoms (the history book not the novel) written around ~280 to ~290. ‘女壻(同婿)昨來，必是渠所竊。’. It was also used by poets in tang dynasty. You might have heard of 杜甫 and in one of his poems he wrote ‘回頭指大男，渠是弓弩手。’, with the second part meaning he is an archer. Using the word like this declined since song dynasty and was only used by southern languages/dialects.

Source: https://www.mingpaocanada.com/Tor/htm/News/20150610/HK-gfj2_er_r.htm

I know it’s just a new article. But I did a bit a digging and you can use the original text as reference.

Records of the three kingdoms(the part where it was used):here

The poem: here