GPT-5.3-Codex came out in February, and GPT-5.5 came out in April. How much better do you expect in two month's time? What other products can you think of that get meaningfully better in that short of a time frame?

And as good as 5.3 Codex is at writing code, 5.5 is easily just as good, if not better. But 5.5 is more than a one trick pony and it is much better at planning, writing copy, documentation, etc. I can choose to run 5.3-Codex instead of 5.5, but I never ever do.