Nonsense.
If they took marriage vows, be them Catholic, Protestant, whatever, they made a vow with their own mouths.
A vow is a vow.
No legal contract is ever considered void because one of the parties later declares that they had no intent on keeping it in the first place, that they went into it with the intent to deceive.
They are still legally bound by the contract they entered into.
The Catholic church is just using weasel words as an excuse to give Catholic couples a divorce, a breaking of the vows they made before their church and GOD, without calling it a sin and without excluding them from participating in church.
After all, if the church stuck to their guns about not breaking marriage vows, they'd be cutting off their noses to spite their face. They'd be alienating those very people they depend on for money.
So.....if you discover that the person that you just married is your sister who was given up for adoption before your mom got married....that is still a valid marriage???