Might have something to do with a post from one of their reps back in 2010:
"TazKristi wrote:
Hey ya'll. Reading through a few different threads this morning and a couple of things popped out at me that I think need to be clarified.
1st - Disassembling a Spyderco voids the warranty. Period. There was a question about this being a "myth". It is not a myth. It does not matter if you don't break anything when you do it. If we can tell that a knife has been disassembled (whether it's a FrankenSpyder or not) the warranty is technically void. We manufacture knives with all screw construction not because we want you to take them apart. We do so, so our Crew can take them apart for maintenance and repair. I'm sure there might be some other questions, but bottom line, if you take your knife apart, the warranty is void."
I'd say thats pretty clear.