Do you have any evidence to suggest the engineers believed that?
So there's direct evidence of Apple insiders thinking Siri was pretty great.
Of course we could assume Apple insiders realised Siri was an underwhelming product, even if there's no video evidence. Perhaps the product is evidence enough?
When it says “please open iPhone to see the results” - half the time I think it’s capable of responding with something but Apple would rather it not.
I’ve always seen Siri’s limitations as a business decision by Apple rather than a technical feat that couldn’t be solved. (Although maybe it’s something that couldn’t be solved to Apple’s standards)