I could think of a few reasons for doing this on a progressive press.
A) using a powder that doesn't meter well, and wants maximum accuracy
B) pushing the upper limits of a powder charge, and accidental overthrows when metering by volume can be dangerous
C) Working up ladder loads for accuracy testing (10 each, for instance), where "resetting" the powder dispenser would be more hassle than it's worth.
So, gain the advantages of auto-sizing/priming with manual powder dump and bullet seat.
If any of the above is the case, skip the powder dump and bullet seat stations on the progressive. Run your brass through to size and prime, then load them up in a tray and finish by hand on a single stage or turret press.
I do this on 223 when I'm loading accuracy loads or ladder testing. Let the progressive walk the brass through two of the steps, finish it off by hand on my turret press.