Your camera is capturing a frame every 4.17 ms
Your sketch is averaging a new frame every 4.88ms
I suspect that what this actually means is that most frames appear at 4.16ms and occasional frames appear at more than 4.88ms.
Easy enough to see with a Logic Analyser.
Bear in mind that the ESP32 will probably be blitting the SSD1306 using DMA.
The ESP32 has lots of other tasks to get on with. e.g. operating the Wireless whether you asked it or not.
Does it matter? A human can't see 240FPS. I don't know how quickly the OLED pixels can actually change.
Monochrome animations work quite nicely on the OLED.
Now run the same animation on a GLCD. You just get a blurry mess.
Regardless of Wireless, it seems unlikely that your 4.17ms period capture would ever catch a 2-pixel change.
If you do not have a Logic Analyser, post your code. Someone might try it for themselves.
David.