When you turn the drive knob up on the Klon, the main clean signal path is also blended out by getting shunted to virtual ground. It definitely becomes a hard clipper as you turn the drive up. I'm sure you know this so I don't know what the disagreement is here.
Does the Kemper Drive exhibit a hard clipping behavior at the high/max drive Klon preset settings?
What does the Slim Down parameter do exactly? Is it simply a boost around 1 kHz?
No, it does not become a hard clipper, because there is a second parallel clean path that stays, because it is not affected by the drive pot.
Named "Network 1" in the electrosmash analysis. And it can easily be heard in the Klon's output.
Btw. the term hard clipper and soft clipper is a bit misleading as used in the Strymon analysis.
Soft clipper is usually the name for a "soft knee" distortion, not for a distortion with a parallel clean path.
Slim Down narrows down the frequency responce around the "Definition" frequency, wherever it's set.