Normally, the HT coil, the points and the condenser are connected together. They may not be obviously, directly connected.. some wire's path might travel though an ignition switch first, for instance.. but for the engine to run the three things are connected.
If you ground the condenser wire the engine dies.. since the condenser wire is connected to the points, you're also grounding the points .. you're also grounding the HT's primary coil. It's the same difference.
Page 78 of THIS manual has a wiring diagram (or see attachment).
It shows two wires at the kill switch. The kill-wire is black. It's appears to be connected to the magneto's blue (points/condenser) wire at the HT coil..
This black wire appears to go through two "terminal blocks" on it's way up to the kill switch (called the "Cutoff switch" on a Batavus).
Funny thing.. Pages 76-77 of the manual instructs making a drawing before removing switches and the wires.. says it can be "very easy to forget how it was once they have been removed".