All my Swatys (both 2 and 3 lines) are great finishing hones. My guess is results somewhere between 9k to 11k (depending on how light a finish stroke you can get). Your Swaty sounds defective or maybe it sat in some chemical for a while.
And whatever you do; do not lap your concrete block lapping device on a sidewalk. Sidewalks are nowhere near flat enough.
Just because some woodworkers, and other old-timers, have used (or do currently use) a concrete block for lapping, is no reason for you to actually try such a simple solution yourself...