Why not GPT-{5.6, 6, 6.1} Sol? They're all cheaper than GPT 5.5, and as "smart", if not "smarter", at least to me.
Though, it has been a while since I've used 5.5.
I have no data to support this, but when working on SaaS systems I find anthropic models more effective.
But for webdev, deep research, code review, and a few other tasks I find the current 6.1 sol better.
But I use both. And I use codex more.
Surely they mean Opus-5.5...