I've only got a 3ph auger, but could've definitely used down pressure as I've had to limit my augering to the months here when when the ground has a bit of moisture in it because our clay becomes nigh impenetrable. When I had to have a hole in mid-August, I literally pre-dug 6" by hand with a pick, filled it with water, and refilled it the next day when the previous water had soaked in (and dried, more probably, in the 10% humidity); then hand-dug down another 6" so that the next soak could be more effective, and only then was the auger without down pressure able to do anything.
I've considered getting a SSQA hydraulic auger at auction as the local-ish place had a bunch a couple months ago. I figure that my augering almost never uses much more than my tractor at idle, so if the gpm of my tractor was a hair low (9.8 vs 10) it should still be fine. The main reason I didn't pull the trigger is that I'm hoping that my augering at this property is mostly done at this point with a perimeter fence being complete. The occasional future hole for trees or whatever will be done in late fall when my 3ph unit is effective.