That's a really interesting question Jess. I have met many young offenders who said that their 'initiation' into sexual activity with an older woman did them no harm, and they felt they had some status amongst their peers. If the same had happened with an older man when they were under the age of consent, they would have seen the experience in a very different light. I only know anecdotally how it impacted on them. Some felt, on reflection, that they had been abused, just as many didn't. Other practitioners will perhaps know more than me about this. I used to tread very carefully about 'enlightening' a young man about such experiences, not wanting to impose a sense of having been harmed by an older woman, but feeling a sense of responsibility to instil some knowledge about being protective when they have children.
Equally, when training multi-agency staff, I and my colleagues heard private disclosures from men who had had the same experiences as boys with adult women. They said they had regarded it as exciting, scary, a rite of passage to brag about (several examples of fancying their friend's mum, being exploited by the woman). Often, the examples were like the schoolgirl/teacher scenario. Pennies dropping like mad when boundaries were clarified i.e. it doesn't matter how provocative a child is, they need guidance not exploitation.
So, I don't really know enough about those who say they didn't feel harmed, but those who did had varied ways of dealing with it, some lashing out, seeing women negatively, some needing counselling or just to talk things over. I wouldn't offer counselling to someone who felt he didn't need it when he recognised he had been harmed, but I would keep a weather eye on him.