Maybe it's an attempt at signaling discretion but don't see it as a strong case, and might better be taken as a red flag signal. If you sign one you've got some very clear evidence that persists. And are you really going to try suing for damages? I suspect that might just cause one more problems than it solves, assuming the court is even willing to hear the case.

 
I would say past behavior is a much more useful signal of discretion.

Her site says "happy to sign and NDA upon request". That leads me to believe someone asked her to sign onc and she thought "hey, this might give me a slight competitive advantage".  But I'm with everyone else - I don't see how asking a provider to sign an NDA gets you much other than maybe some psychological comfort.

I've offered NDA's & never been asked to sign any.

Over twenty years now & it's all trust. I have never shared anything personal about my friends it's a mutual respect. No NDA's needed. No Diddy. 😂