I hate using OP machines, and no they don't absorb all the soil load.
Yes some goop is sucked up into the pad or bonnet but not 1/100 of what HWE pulls out. The days of the OP hucksters selling you thousands of pads are gone, have you noticed?
No one was flipping and changing their cotton op pads like they should have (one side every 20 sf or so) so they went to more aggressive synthetic pads and more polymer in the juice to better break loose and HIDE the soil load. Now a daysn the OP gawd make their revenue on over priced juice and grossly overpriced machines that need replacing every 8 months due to planned obsolescence..
The manufacturers had a heck of a time finding a cotton pad that would work with a Velcro type driver without destroying the pad in a few uses. Now we see bristle type drivers pushing micro fiber pads and are told to believe that a whole home's worth of soil is being contained in the foam inside the pad..

Some HWE die hards will never come to terms with using magic to "clean" Carpet,
Saiger, Erik, Lockhart for example.
Me?
I prefer to grind away on commercial with a Cimex and post pad the gooey areas with a 175 when needed.
OPs with spray ahead systems and I don't get along. YMMV.