I wanted to but couldn't find a better title

So while leafing through Thomas W. Hale's Medication and Mothers' Milk (12th edition), I found that fenugreek is an L3, fennel is an L4, and blessed thistle is an L3. I found this puzzling. Is it because they're herbs and not so many studies have been done on their use and effects, etc.? (domperidone, the reason why I opened this book, is a bright shiny L1)

Also Dr. Hale wrote that fennel "may potentially suppress milk production" because "it is primarily believed to be estrogenic" (page 339). Then WHY is it one ingredient in Mother's Milk Tea (and IIRC some other lactation-support products)??