I find the last comment non-feasible. Such offenders are lying.
My father did extensive work with sex offenders in Australian prisons. He says that all sex offenders were addicted to porn. They get addicted so much that just like drug users the existing 'fix' is not enough. So they increase the dose. For sex offenders this means going from visual imagery to people. He says that there is no safe level of porn for anyone.
I could see an argument that for a horny college kid, porn might prevent them from getting out of hand while drunk and date-raping a girl. But not for sex offenders. Like you said, it doesn't seem to work that way, unless the "researcher" is trying to support a pre-existing belief.
It's up there with the people preaching that "Sex Work is Work", and pretending that legalizing prostitution is "empowering" to women... while simultaneously ignoring that legalized prostitution increases human trafficking for the purpose of sexual slavery and makes it legal to exploit vulnerable people.