I think they are the same model and it is just a massive load difference. I kind of thought that might be the case originally. It makes total sense that this mysterious model was processing at blazing fast speeds. It was kind of hinting that a behemoth provider was serving it behind the scenes.

Another reason I think tehy are the same model is that plan mode for me in cline never works properly with horizon beta and neither does GPT5. Those are the only two models that seem to have trouble with plan mode.

I think there are too many coincidences that line up and that horizon models were almost certaintly GPT5.