But again, they should be honest with their guests, it is their guests business, and if their guests can then make a decision themselves on spend and attendance based on their own subjective opinions and feelings.
Of course not, why would they need to?
YOU decide that the only important and valid part is the legal ceremony. Again, many people believe it's just a formality, which means nothing and don't feel married or committed by signing a vague piece of paper.
For these couples, the REAL wedding ceremony is the one in church, (or a humanist ceremony in a significant place, or whatever they believe in).
Why do you think it's any of your business to decide it's valid or not? It's their wedding, they invite you to what they believe is important, I stand by my point, it's none of your business and not up to you to decide they are wrong, and it doesn't count.
You can easily divorce from a legal wedding, it's not the same for some religious ones.
I don't believe it's manipulating anyone, or that everyone has to go into full details. I don't believe it's any of the guests business if the couple had sex before, will have sex on the wedding night either.
I honestly do not understand what the big deal is.