This is 100% true for Europe.
I think you didn't put enough attention to the however segment.
Age gaps did happen, for sexual encounters, and casual sex was common.
But it wasn't common for young women or old men - the two groups who evidently had the most extramarital sex were unmarried men under 25 and married or widowed/single women over 35.
This was extremely common.
I went down this rabbit hole and discovered that whereas most older men seem to want a younger partner, women are more likely to have actually had or pursued significantly younger partners.
The reaction then was the same as now - if you heard that a 17 year old girl was fucking a 23 year old man, it would be weird now and was weird then.
But the alternative, a 17 year old boy fucking a 23 year old woman, was Henry VIII's first marriage! And he was well-liked for this, being seen as a handsome and masculine king for it.