GxEPD2 Partial refresh takes 3 seconds instead of 0.3 seconds. How come?

[toddnz]

@Thomasx

When reading the Waveshare spec (link below) on my display, it says partial refresh takes 0,3 seconds, but when I do a partial refresh, it takes almost exactly 3 seconds.

I believe Waveshare is only counting the time taken for the display image to change, not any time you take rendering / transferring the image.