I read somewhere that the use of "A" for alpha in Chinese culture comes from Japanese application of American-originated A/B/O porn tropes to BL porn
I don't have a way to verify this but it is hilarious if true
Yeah, it's hilarious because nowadays it's completely acceptable for any normal person to call someone an A or B. Although compared to the west the connotation is a bit different, calling someone an "A" is basically calling someone a "Chad" imo.