I mean sedimentary in geological terms - "rocks formed by the accumulation of fragments, or the precipitation of dissolved material, that result from the weathering of pre-existing rocks".

Granted sarsen is an extremely hard quartz sandstone but it is still a sedimentary rock.

What I was suggesting was that do the features that have been proposed as being man made occur on igneous standing stones?

As for how many hours to produce a polisher stone, I think you need to think in terms of months and years depending of the harness of the material that you are polishing and the abrasive medium used. I'm sure that they would have used different grades of abrasives e.g. a coarse quartz sands grading down to fine sands depending on the stage of the polishing process and the finish required.
I have a sharpening stone at home that belonged to my grandad and has lost about 1 cm of depth in 70+ years of sharpening steel knives.