Even if there was a way for you to sign without seeing the documents you are normally liable if you sign a document which is why you should always ask to see what you are signing. This is a complex situation which is why consulting a lawyer about how to address the issue with IRCC would probably be best.
So your answer to the first is 'no', you do not know for a fact that the applicant must physically/electronically see the thing.
And yes: it is complicated. And yes: agree with comment about a lawyer.
But my point remains: despite the overall principal 'in law' that when you hire someone to represent you, you take responsibility for their actions, 'the law' is rarely quite so absolute about this as the hairshirt crowd (you know how you are*) want to paint it.
The presumption is that you are responsible for your hired representatives. But as I pointed out, there are a) mechanisms to enforce that presumption (eg the old practice of publishing or 'gazetting' certain public notices, and those who don't check the gazettes are presumed to not have done the minimum of research required, and conversely - if you don't make those public notices, you are deficient); b) higher and often much higher requirements made for certain licensed professionals as well as enforcement mechanisms for those professions, and c) exceptions made for when certain licensed practitioners have broken those rules/violated the rules of their profession. Because they're considered exceptional.
Or as applies to this case: it seems there was a lawyer/licensed professional involved (not certain about this), AND the applicant pursued the case in court. And there was at least some real threat of a penalty for that lawyer. It doesn't fit the profile - at least entirely - of "I hired a consultant and he just wrote whatever, how could I know?". Not saying it's clean cut, but that's the point.
*Actually you probably don't and think you're moderates.