It's the lever ratio that magnifies any discrepancy. There's the exact position of the port, the seal, the piston length, the push rod length, and the lever pocket and pivot position. The overall stacked length, actually involved, can vary by 1-2mm easy, just 0.5mm on each part for example. I've no issue with the OEM cylinder once the pads engage, and the 19mm version is even nicer, it's just the variability in the feel one unit to the next. Still, if you can be bothered, the adjustable push rod mod cures it.