in the book 類篇 卷二十二 (page 87 of the liked pdf), there was an entry:
that, 伲 儞 你 ・[these three characters are pronounced as] 乃倚切・[have the meaning of] 汝 (you)
the book “類篇” is edited between 1039-1066, in 宋 dynasty.
i would say that 儞 / 你 existed in the past, just not commonly used as 汝
have fun :)
儞 is an archaic classical term that had been replaced by 你 in traditional character. ("long before simplified Chinese" was introduced." as one of your reference stated).
In other words, when they started simplifying traditional characters, the character 儞 did not exist in modern Chinese. It had been simplified to 你, and the ...