Ah! I had assumed that the hive-Shae was created soon after the False Sun, but as you say, maybe not!
I love the idea that Seswatha dealt a massive blow to Shae to cause Shae's form..."your accurshed tutor..." I hope we get a flashback on that.
However, Akka seems to think that the circle IS the method by which Shae persisted all those years. If Shae hadn't yet employed that method, I wonder how he was cheating death before the battle with Seswatha.
Perhaps he had already moved into a hive shape, but still had all limbs and such, then Seswatha burned him.
ALSO, thinking about The False Sun and then the Ch 1 excerpt, I think Aurang and Shae's lovelife has taken a dive

...or gotten kinkier?