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I don't know about the 533 as I have never used one but that is not the case with my pigeon pair of 2600MM and 2600MC. I shoot dawn sky flats and aim for 32K ADU (With a 15% tolerance to avoid it chasing exposure times and repeating the same flat) and the exposure times vary from around .2 seconds to 30 seconds or more depending on how close to sunrise it is and the filter being shot. I calibrate the flats with a master bias.
The biggest impacts I have found on flats is that a 32 bit master bias is better, and the lights need to also be calibrated with a master dark matching the exposure and temp, preferably a 32 bit one. I recently completed some unintentional testing where I was having issues with over corrected corners and in terms of quality of flat field correction it was (From worst to best) light frames calibrated by:
*Master flat (32 bit) which was calibrated by an older 16 bit master bias. Lights calibrated by the master flat and by the same master bias. Very visible brightening in the corners that required a significant crop to avoid.
*Master flat (32 bit) calibrated by a 32 bit master bias, lights calibrated by the master flat and a 16 bit master darks. A big improvement in the corners.
*Master flat (32 bit) calibrated by a 32 bit master bias, lights calibrated by the master flat and 32 bit master darks. A smaller improvement in the corners compared to the one above, good enough that I only cropped out the area where the effect of dithering was visible.
All of the above used the same flats and lights.
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