Note carefully that Borg's criterion is NOT merely a criterion for doubting a given saying. It is a criterion for positively DENYING such saying.
The ACIM partisan may clap and condescendely smile when he see liberals dismissing John's Gospel with such arguments like Borg's, but it only exposes the partisan's own methodological inconsistency, obvious double standard, self-deception, intellectual superficiality and egregious disregarding for the truth.
Emotion and wishful thinking seem to have priority here.
Otherwise, he would see that the main arguments and methodology used by liberals like Borg (specially extremistic ones like those in the Jesus Seminar) against John's Gospel would ALSO destroy the credibility of ACIM.
Since Borg's criterion is NOT a criterion of meaning, hemeneutics or biblical exegesis, but a criterion about what's historical, Borg's objection cannot be sympathetically accepted by the ACIM partisan as applied to John, but skip it entirely if applied to ACIM.
Fact is that, if ACIM actually comes from Jesus, it provides independent attestation of such saying in John, and hence Borg's speculative objection cannot be accepted by a consistent believer in ACIM.
So, we have another independent attestation, by a putative independent source, confirming the utterance in John's Gospel.
But why exactly Jesus' nature must fit Borg's (or any other liberal scholar) naturalistic-atheistic framework? (The same question applies, of course, to the framework of Christians, Jews, Muslims and others... precisely for this reason we have to examine the EVIDENCE regarding Jesus in the New Testament).