That is a good point... the relationship part is inherantly subjective.
There's also the intent to settle in Canada bit.
Is that all, though?
Yup - it's purely based on the criteria in the checklists and further detailed primarily in IP-2, OP-2.
What if they just don't like the cut of your jib?
That is not sufficient reason to reject you. CIC really is good about establishing set criteria - and publishing them for all to see - and if you pass each step you make it through to approval.
And, then, if the VO were to go crazy right before reviewing your app, you can write to the program manager and ask them to reconsider, and if they went crazy too simultaneuously you can appeal.