I'm pretty sure I had to sign NDAs regarding coding questions before any interviews happened (not Amazon, a different company).
It's the difference between a polite "this offer doesn't work for me at the moment", and burning your bridges.
(However, this particular article doesn't seem to discuss any specifics of technical questions, so I don't see an issue here)
Usually they mention any sort of business practices or plans you might learn about in the course of interviewing; recruitment is highly unlikely to fall under that definition.
I don't share questions as a matter of principle, fwiw.