You are missing that 3s are done because it allows a heavier weight so your premise is incorrect. It is also important to understand that 5s are not standard for women. Women have a different pattern of motor unit recruitment that men and need a bit more stimulus to recruit the highly fatiguing high threshold motor units. You and I can effectively do this with sets of 5. Fairly early in their training progression women no longer can. We therefore switch them to 3s in an attempt to produce the same sort of neuromuscular stimulus that you and I get from 5s.
So no, in this case a set of 3 for her is in every acceptable use of the term, a higher intensity stimulus than a set of 5.