Except the problem for you is that the Emperor is just saying that they are all as bad as each other. Not confusing one with the other, really. Why would you think that was the case?
Because of the variant of the letter where Chrestians is rendered Chr
istains and Chrestus is Christ:
"Egypt, which you commended to me, my dearest Servianus, I have found to be wholly fickle and inconsistent, and continually wafted about by every breath of fame. The worshipers of Serapis (here) are called
Christians, and those who are devoted to the god Serapis (I find), call themselves Bishops of
Christ are, in fact, devotees of Serapis. There is no chief of the Jewish synagogue, no Samaritan, no
Christian presbyter, who is not an astrologer, a soothsayer, or an anointer. Even the Patriarch himself, when he comes to Egypt, is forced by some to worship Serapis, by others to worship
Christ. They are a folk most seditious, most deceitful, most given to injury; but their city is prosperous, rich, and fruitful, and in it no one is idle."
Now compare that version to the one that was often quoted over 100 years ago:
"Egypt, which you commended to me, my dearest Servianus, I have found to be wholly fickle and inconsistent, and continually wafted about by every breath of fame. The worshipers of Serapis (here) are called
Chrestians, and those who are devoted to the god Serapis (I find), call themselves Bishops of
Chrestus are, in fact, devotees of Serapis. There is no chief of the Jewish synagogue, no Samaritan, no
Chrestian presbyter, who is not an astrologer, a soothsayer, or an anointer. Even the Patriarch himself, when he comes to Egypt, is forced by some to worship Serapis, by others to worship
Chrestus. They are a folk most seditious, most deceitful, most given to injury; but their city is prosperous, rich, and fruitful, and in it no one is idle." (Drews, Arthur (1912)
The witnesses to the historicity of Jesus)
Somebody is being cute with the translation and given what happened with Josephus it doesn't take an Einstein to figure out who.