That's just plain wrong. At least, the fact that a marriage lasted a long time only weighs on the side of validity. It is NOT a conclusive piece of evidence. Either the priest they talked to was careless in his speech, or the women misunderstood what they were being told. It is true that adultery that starts immediately after the wedding is evidence of nullity, while adultery that starts only after 30 years is not. But discovering the truth is what the annulment process is all about.
The people at this meeting were worried about paying a large sum of money to go through the annulment process, only to be denied an annulment in the end.
According to what I've read, the reason Pope Francis is bringing up the annulment process as an issue is that he once fired an official who was overcharging for it.
Anyway, that's why I'm in favor of Pope Francis addressing this topic. Thank you for your feedback, Father. Have a good night.