What are the differences of the four sentences?

In 1, 2, and 4 both people are wrong. But in 3, one person is wrong.

What do you think of the following opinion?
https://english.stackexchange.com/questions/540900/are-the-following-four-sentences-the-same-in-meaning

Neither you nor he is right.
Not either you or he is right.
Either you or he is not right.
Both you and he are not right.

Examples 1, 3, and 4 are grammatical; example 2 is not. ("Not either" = "Neither")

Examples 1 and 4 both mean the same thing, i.e., that both individuals are wrong (although some may argue that the two statements have differing connotations or emphases).

Example 3 does not mean the same thing as 1 and 4, but instead posits that only one person is wrong instead of both.

I didn't mean to imply that Example 2 is right, only that it is an ungrammatical way of stating what Examples 1 and 4 say.

Sorry if I confused you.

Thank you very much for your kind answer.