There is another way to look at this. Jesus was not making an exception he was throwing down the gauntlet against the demons in Gerasenes, gentile territory .
In Mark we see two examples of Jesus confronting demons. In one case in Jewish territory:
Leave us alone⌋, Jesus the Nazarene! Have you come to destroy us? I know who you are—the Holy One of God!” (Mark 1:24 LEB)
In this verse Jesus is addressed as the Holy One of God and it would appear that the demons fear being destroyed, for me this makes sense, Jesus can destroy these demons…
The other case Gentile territory
And crying out with a loud voice he said, “⌊What have I to do with you⌋, Jesus, Son of the Most High God? I implore you by God, do not torment me!”(Mk 5:7 LEB)
What did the legion fear death? No it was torment. How can you torment a demon? From the verse it appears he feared being sent out of the region. Why would this matter, a demon is a demon is a demon?
And he was imploring him many times that he would not send them out of the region. (Mk 5:10 LEB)
Now to the delivered lunatic. Jesus wanted him to tell everyone want Messiah had done for him in what was known as the unholy Bashan territory. The Most High was going to reclaim the world, all of it. This man was to spread the word in the Decapolis area and lets no forget that the incident had already been well reported to town and country side.
14 And their herdsmen fled and reported it* in the town and in the countryside, and they came to see what it was that had happened. (Mk 5:14)
This will be a bit different then how you would normally read these verses. I have shared with you the thoughts of Michael Heiser. This is my understanding of how this verse would be understood by the Jewish reader of the day:
From Reversing Mount Hermon:
“The exorcism of Legion is therefore more than a strange tale of suicidal swine. It’s about theological messaging. Legion recognizes that Jesus is rightful Lord of the country of the Gerasenes—old Bashan now under Gentile occupation.”
Heiser, M. S. (2017). Reversing Hermon: Enoch, The Watchers & The Forgotten Mission of Jesus Christ (p. 101). Bellingham, WA: Lexham Press.
I really would be interested in the communities thoughts on this.