My sister-in-law just lost her marriage to porn. Her husband seemed incapable of telling the truth about anything.
The same thing was true of a pastor my husband used to work with, who was found to be viewing porn on the church’s computer. He was forced to resign because of several affairs but even months after he supposedly came clean with his wife she didn’t know he had had multiple affairs. She found out at a meeting she called for leaders in the church. He was seemingly incapable of telling the truth - not just about the porn stuff but about even simple things like who he had visited and what they had talked about.
I don’t know exactly what the power is, but porn does mess with a person in deep ways, and not the same as other addictions.
Another way to look at it, perhaps, is that your sister-in-law didn't lose her marriage to "porn," but lost her marriage because the person she chose to marry was a liar.