I'm a Canuck, so centuries of legal, common law separation here...
But if someone misrepresents what a contract is, and even more so applies pressure to sign, it's meaningless.
My understanding is that this goes back to "make your mark" and lower levels of literacy, and in modern times, that legalese is gibberish to many, thus misrepresenting what you're signing can effect enforcement/validity.
It's very stupid for them to brush it off like that.
(I wouldn't have signed either, and have walked from jobs and contracts over absurd NDAs. One client actually wanted me to sign a forever NDA, but 1/2 way through the contract! Wtf?! Negotiate that at contract sign, not months later!)