Kernel crash dumps and swap

[John Dison]

Hello,according to Chapter 10. Kernel Debugging
"The dumpon(8) program must be called after the swap partition has been configured with swapon(8)."

This sounds ridiculous: why should I enable swap in my system in order to be able to obtain a crash dump?Isn't it a mistake in documentation?
I understand that I must label swap partition, but actually *enabling* swap looks unrelated to crash dumps.
Thanks.