I thought when the ABC system was taken up about 50 years ago the brass cylinders were effectively 'finished' & simply 'flashed' with hard chrome .. one or two tenths. No post-chrome honing or lapping, the desired geometry set in the brass. Also believe it's the initial tenths are the hardest?
Not sure about 50 years ago but the last 30 or so anyway it's been about 0.002" of finished hard chrome (1100 Hv) per side.
Lots of other two stroke stuff with rings have flash plated Nikasil cylinders.