They did compare it to other models: https://x.com/OpenAI/status/1999182104362668275
The fact that the post is comparing their reasoning model against gemini 3 pro (the "non reasoning" model) and not gemini 3 pro deep think (the reasoning one) is quite nasty. If you compare GPT5.2 thinking to gemini 3 pro deep think, the scores are quite similar (sometimes one is better sometimes the other one is)
This looks cherry-picked, for example Claude Opus had a higher score on SWE-Bench Verified so they conveniently left it out, also GDPval is literally a benchmark made by OpenAI