Is the response of Gemini 2.5 flash image slower than that of Gemini 2.5 flash image preview? Analysis of technical reasons

When we call Gemini 2.5 Flash Image and Gemini 2.5 Flash Image Preview, we find that the response time of the preview version is 4-5 seconds faster than that of the official version. We are not sure what causes this issue—logically speaking, shouldn’t the official version perform better than the preview version?