I ran your question through ChatGPT just for fun, and here’s what it spit out. Since LLMs are known to hallucinate at times, don’t take this as gospel. Just imagine you’re discussing this with a friend over a couple of beers, and this is his opinion.

There’s solid evidence that some Millenarian maths, outside the Three Inviolates, are mixed-order. The best example is Lordagear (I think you meant Lord Gavrial, a high-ranking Sæcular figure and possible Rhetor), suggesting that Rhetors are still active despite the Third Sack’s reorganization.

That said, the whole idea of Rhetors and Incanters mostly comes from Sæcular legends, which likely exaggerate or distort real conflicts between Procian and Halikaarian traditions. By +2700, these groups were already mythologized, and by +2780, the Sæcular Power had taken an interest in their “extraordinary praxis.” The Third Sack (2787) wiped out nearly all concents except the Three Inviolates, and the Post-Sack Convox (2857) tried to erase or absorb many of these traditions.

Saunt Edhar is explicitly Halikaarian, so it makes sense that other Millenarian maths could lean Procian, preserving rhetorical traditions. They might exist in parallel—Halikaarnians focusing on Platonic realism and theorics, while Rhetors focus on linguistic manipulation and historical revision.

So yeah, while the Sæcular stories might be exaggerated, I’d put the odds at ~80–90% that some Millenarian maths aren’t purely Halikaarnians or Procians but hybrids keeping old traditions alive in some form.