> Deprecating GPT-4.5 less than 2 months after introducing it also seems unlikely to be the original plan.

Well they actually hinted already of possible depreciation in their initial announcement of gpt4.5 [0]. Also, as others said, this model was already offered in the api as chatgpt-latest, but there was no checkpoint which made it unreliable for actual use.

[0] https://openai.com/index/introducing-gpt-4-5/#:~:text=we%E2%...