Here’s some context that you may find useful:

It’s not exactly a kill switch, though it could be viewed as similar.

If the node runner does not update the Knots software for a number of years (five years, I believe) it displays a dialogue that asks the user if they would like to continue running the old software. If the user answers no or does not respond, Knots automatically shuts down.

This timer resets when the node runner updates the software. So most people never see it.

The reason this is in the Knots software is because—at some point—outdated software becomes a security issue (to be clear: not a security issue for the Bitcoin network, but for the node operator).

Additionally, if the user has not updated their node software in a number of years, it’s probably a node they left running in their basement or something and forgot about.

So Knots turns off once it becomes outdated, unless the node runner explicitly tells it to keep running.

Not making an argument for or against any node implementation or telling anyone what to do. Just a better explanation of how the function works in practice and my understanding of why it’s in the Knots software.